EXCHANGE 


EXCHANGE 
MOV  16 


THE  COKING  OF  COAL  AT  LOW  TEMPERA 
TURES  WITH  SPECIAL  REFERENCE  TO 
THE  PROPERTIES  AND  COMPO- 
SITION OF  THE  PRODUCTS 


BY 


HUBERT  LEONARD  OLIN 

B.  A.  University  of  Iowa,  1908 
M.  S.  University  of  Illinois,  191 1 


THESIS 

Submitted  in  Partial  Fulfillment  of  the  Requirements  for  the 

Degree  of  Doctor  of  Philosophy  in  Chemistry  in  the 

Graduate  School  of  the  University  of  Illinois 

1914 


THE  COKING  OF  COAL  AT  LOW  TEMPERA- 
TURES WITH  SPECIAL  REFERENCE  TO 
THE  PROPERTIES  AND  COMPO- 
SITION OF  THE  PRODUCTS 


H.  L.  OLIN 


CONTENTS 

PAGE 

I.     INTRODUCTION 3 

1.  Preliminary  3 

2.  Resume  of  Previous  Work . .  3 

3.  Outline  of  Present  Investigation 4 

II.     EXPERIMENTAL  WORK 4 

4.  Description  of  Coking  Oven 4 

5.  Coking  Tests  6 

6.  Gas  Producer  Tests  11 

7.  Adaptation  of  the  Coke  to  Domestic  Appliances ....   18 

8.  The  Sources  and  Uses  of  Coal  Tar 18 

9.  Methods  for  Testing  and  Analyzing  Tars 19 

10.  Properties  of  Tar  Products  From  Low  Temperature 

Coal   Distillation 20 

11.  Distillation  of  Tar 21 

12.  Examination  of  Light  Oil 22 

13.  Examination  of  Heavy  Oil  Fraction 25 

14.  Pitch 26 

15.  Oxygen  Absorbing  Power  of  Tar 27 

III.  APPENDIX  OF  SUPPLEMENTARY  RESULTS 27 

IV.  SUMMARY  ". 29 

V.     REVIEW  OF  LITERATURE  . ; .'. V^. ;  /„.; \, . ; : 30 


314802 


ACKNOWLEDGMENT 

The  writer  takes  this  opportunity  of  thanking  Mr.  A.  P.  Kratz  for 
his  help,  cheerfully  and  generously  given,  in  conducting  the  gas- 
producer  test  which  is  included  in  the  work  covered  by  this  report. 

To  Professor  S.  W.  Parr,  in  whose  laboratory  the  author  has  spent 
the  three  years  of  his  graduate  work  and  under  whose  direction  the 
work  was  done,  he  owes  a  special  debt.  Professor  Parr's  qualities  of 
thorough  scholarship  combined  with  rare  tact  and  human  kindness 
have  made  the  association  doubly  profitable  and  pleasant. 


THE  COKING  OF  COAL  AT  LOW  TEMPERATURES  WITH 

SPECIAL  REFERENCE  TO  THE  PROPERTIES  AND 

COMPOSITION  OF  THE  PRODUCTS 

I.    INTRODUCTION. 

1.  Preliminary. — This  report  covers  a  series  of  studies  made  dur- 
ing the  period  from  1911  to  1913  on  the  coking  properties  of  Illinois 
coal.    It  is  a  continuation  of  the  work  described  in  Bulletin  No.  60  of 
the  University  of  Illinois  Engineering  Experiment  Station.*    Its  dis- 
tinctive feature  has  been  the  use  of  an  apparatus  which  would  yield 
the  main  products  of  coke,  gas,  and  tar  in  quantities  sufficient  for  a 
detailed  study  of  these  products,  and,  to  a  certain  extent,  quantities 
sufficient  for  a  determination  of  their  values  by  practical  tests  on  a 
commercial  scale. 

2.  Resume  of  Previous  Work. — In  the  experiments  described  in 
Bulletin  No.  60  the  apparatus  used  had  a  capacity  of  6  to  8  pounds 
of  coal  at  a  charge.     Notwithstanding  this  limited  capacity,  certain 
fundamental  facts  were  developed  as  follows : 

(a)  The  formation  of  coke  depends  upon  the  presence  of  certain 
constituents  having  a  melting  point  which  is  lower  than  the  temper- 
ature at  which  decomposition  or  carbonization  takes  place. 

(b)  Oxidation  of  these  compounds  may  easily  take  place  and  the 
greatest  coking  effect  is  obtained  where  the  opportunity  for  the  mini- 
mum amount  of  oxidation  has  occurred.     The  condition  prescribed, 
therefore,  is  that  there  shall  be  the  least  possible  exposure  to  oxidation 
either  before  or  during  the  process  of  carbonization. 

(c)  Coals  containing  an  excessive  quantity  of  the  coking  sub- 
stance produce  a  light  porous  coke.    The  texture  of  the  product  may 
be  modified  by  use  of  pressure  and  by  close  packing  of  the  charge  and 


*The  Coking  of  Coal  at  Low  Temperatures,  by  S.  W.  Parr  and  H.  L.  Olin. 

3 


,    v.     .    c-a    »   *•«>  ->      i     ->    '   \ 
4  OLIN  --THS  COKING  OP  COAL. 

especially  by  mixing  with  material  which  has  already  passed  through 
the  coking  process.  Such  a  mixture  provides  the  physical  conditions 
whereby  the  gases  formed  may  readily  pass  out  of  the  mass  without 
carrying  along  the  cementing  substances. 

(d)  By  use  of  temperatures  between  400°  and  500 °C.  all  of  the 
resulting  products  are  of  a  type  distinctly  different  from  those  ob- 
tained by  the  usual  high  temperature  procedure. 

3.  Outline  of  Present  Investigation. — An  apparatus  was  designed 
to  utilize  about  100  pounds  of  coal.     Experience  in  the  use  of  the 
apparatus  indicated  also  the  main  principles  which  should  be  em- 
bodied in  a  commercial  equipment.    The  coking  process  was  studied, 
anc}  the  mixture  for  producing  the  best  product  determined.    It  was 
found  that  a  smokeless  fuel  may  be  produced  especially  well  adapted 
to  domestic  purposes,  including  its  use  in  open  grates.     Its  freedom 
from  tar  or  condensable  hydrocarbons  makes  it  easily  -adapted  to  gen- 
erating producer  gas,  thus  affording  a  good  substitute  for  anthracite 
coal  in  suction  gas  producer  practice. 

In  the  study  of  the  composition  and  properties  of  the  tar,  this  ma- 
terial was  found  to  have  a  very  low  content  of  free  carbon,  a  relatively 
high  percentage  of  light  boiling  distillate,  and  an  unusually  high  con- 
tent of  tar  acids  or  phenols.  The  latter  fact  is  of  special  interest  to 
the  wood  preserving  industry. 

II.     EXPERIMENTAL  WORK. 

4.  Description  of  Coking  Oven. — The  apparatus  used  in  the  ex- 
periments is  an  elaboration  of  that  employed  in  1910,  described  on 
page  5  of  Bulletin  60,  and  is  capable  of  producing  material  in  greater 
quantities  than  was  possible  with  the  older  type. 

The  device  was  manufactured  by  Burr  and  Company  of  Cham- 
paign, Illinois,  and  is  illustrated  in  Fig.  1.  As  shown  in  the  detailed 
diagram  Fig.  2,  it  consists  of  a  boiler  plate  shell  A,  lined  with  asbestos 
to  prevent  excessive  radiation  of  heat ;  within  this,  forming  the  coking 
chamber,  is  a  shell  B  of  the  same  material  containing  a  cone  of  light 
sheet  iron  C,  perforated  with  3/16  in.  holes,  designed  to  confine  the 
coal  charge  and  to  allow  a  free  circulation  of  gases.  To  obtain  the  non- 
oxidizing  atmosphere  such  as  was  used  with  the  old  apparatus,  steam 
was  admitted  from  the  high  pressure  main  at  E,  passed  through  the 
coil  F  where  it  was  superheated  by  the  hot  currents  ascending  from  the 
gas  burner  and  then  conducted  into  the  coking  chamber.  The  heat  was 
supplied  by  a  blast  ring  burner  D,  connected  with  the  gas  and  air 


OLIN — THE  COKING  OF  COAL 


FIG.  1.    APPARATUS  FOR  Low  TEMPERATURE  DISTILLATION  OF  COAL 


6  OLJN — THE  COKING  OF  COAL 

mains,  and  no  difficulty  was  experienced  in  producing  the  desired  tem- 
peratures. The  charge  of  crushed  coal  was  fed  into  the  hopper  G-  and 
admitted  to  the  retort  through  a  large  gate  valve.  The  coked  residue 
was  removed,  after  cooling  the  apparatus,  through  the  bottom  at  H. 
Gases  of  combustion  escaped  through  the  opening  J,  which  was  con- 
nected with  a  flue,  while  the  distillates  were  conducted  through  an 
outlet  pipe  to  a  condenser  consisting  of  several  four-foot  lengths  of 
inch  pipe  connected  by  return  elbows.  Cold  water  was  allowed  to 
drip  over  this  gridiron-like  contrivance.  The  tars  were  passed  through 
a  water  sealed  exit  at  the  bottom,  while  the  gases,  fairly  clean,  were 
collected  in  a  gasometer. 

5.  Coking  Tests. — To  study  further  the  coking  qualities  of  Illinois 
coals  at  temperatures  ranging  from  400 °C.  to  500 °C.  and  to  obtain  a 
quantity  of  the  coke  residue  sufficient  in  amount  for  practical  tests  in 
order  to  determine  its  commercial  value,  a  series  of  runs  was  made 
using  the  apparatus  described.  Numerous  coals  from  the  different 
fields  of  the  State  were  included  in  this  set  of  experiments.  In  this  re- 
port, however,  products  from  representative  types  only  are  illustrated 
and  described  since  the  results  of  tests  of  different  coals  of  a  given 
field  showed  little  variation.  Of  particular  interest  during  the  process 
of  distillation  was  the  behavior  of  the  coals  from  the  northern  districts, 
especially  those  from  Vermilion  County.  As  the  heating  progressed,  a 
black  pitchy  substance  dripped  from  the  joints  of  the  containing  ovens 
but  it  hardened  immediately  on  cooling,  forming  a  brittle  mass  much 
resembling  asphalt.  This  was  undoubtedly  the  cementing  principle 
which  is  instrumental  in  forming  coke.  According  to  Lewes  it  consists 
of  substances  derived  from  the  resins  of  the  original  coal  sources,  which 
melt  at  about  300 °C.  and  decompose  at  slightly  higher  temperatures 
yielding  on  the  one  hand  liquid  products  which  distil  out  as  tar  vapors 
and  hydrocarbon  gases,  and  on  the  other,  a  pitch  residuum,  which  at 
500° C.  forms  a  mass  of  coke.  His  general  theory  that  these  resinic 
substances  are  readily  oxidizable  and  in  their  oxidized  condition  have 
much  to  do  with  coke  formation  is  borne  out  in  these  experiments  by 
the  fact  that  no  weathered  coal  of  any  type  produced  the  gummy  ex- 
udation mentioned,  although  there  was  no  apparent  diminution  in  the 
amount  of  gases  given  off.  Compared  with  the  bituminous  coals  of  the 
Eastern  States,  those  of  Illinois  are  exceedingly  rich  in  this  resinous 
binding  material.  Even  those  from  the  southern  districts  of  the  State 
while  not  as  "fat"  as  those  from  Sangamon  and  Vermilion  Counties, 
nevertheless,  much  surpass  in  this  respect  coals  like  the  Pocahontas, 
and  those  from  Ohio  and  Pennsylvania.  Strangely  enough  the  abun- 


OLIN — THE  COKING  OP  COAL, 


FIG.  2.    CROSS  SECTION  OP  APPARATUS  FOR  Low  TEMPERATURE  DISTILLATION 

OP  COAL. 


8  OLJN — THE  COKING  OF  COAL 

dance  of  the  coking  material  which  the  western  types  possess  is  the 
cause  of  their  inferiority  in  the  matter  of  making  dense,  hard  coke ;  for 
with  the  decomposition  of  the  resinic  bodies  and  the  deposition  of 
cementing  carbon  there  occurs  at  the  same  time  an  evolution  of  large 
quantities  of  gases  which  inflate  the  pasty  mass  and  make  the  result- 
ing coke  more  or  less  light  and  spongy.  Indeed,  certain  Vermilion 
County  coals,  after  being  heated  under  conditions  which  allow  free  ex- 
pansion, present  the  appearance  of  hardened  froth,  because  of  the 
excessive  development  of  cell  structure  in  the  coke. 

As  has  been  shown  in  the  previous  work  the  porosity  of  the  product 
may  be  appreciably  reduced  by  subjecting  the  contents  of  the  oven 
during  the  heating  period  to  a  considerable  pressure.  Another  means 
to  the  same  end  which  was  recognized  in  the  first  experiments  and 
which  has  been  applied  in  the  latter  series  is  the  addition  of  inert  coke 
dust  to  the  raw  coal  as  fed  into  the  retort.  This  material  acting  in  the 
capacity  of  a  "blotter"  reduces  the  plasticity  of  the  softened  mass  and 
allows  the  gases  to  escape  freely  without  producing  a  blowing  effect. 

The  diluting  medium  in  the  case  of  the  specimens  shown  here  was 
a  mixture  of  various  semi-cokes  which  had  accumulated  in  the  course 
of  the  work.  The  material  was  crushed  and  ground  to  a  fineness  of  40 
or  50  mesh  and  thoroughly  mixed  with  the  rest  of  the  charge  in  ball 
mills. 

An  analysis  of  a  composite  sample  of  this  semi-coke  breeze  gave  the 
f ollowing  results : 

TABLE  1. 
COMPOSITION  OF  INERT  COKE  MIXTURE. 


Actual 

Dry 

Moisture 

1.85 

Ash 

11.90 

12.15 

Volatile  Matter 

19.85 

20.22 

Sulphur 

2.62 

2.67 

Fixed  Carbon 

66.40 

67.65 

Calorific  Value   (B.  t.  u.) 

11243 

11454 

The  effect  of  the  addition  of  this  foreign  substance  is  exceedingly 
interesting.  Certain  types  of  coal,  as  for  instance  those  from  Ver- 
milion County,  produce  hard  firm  coke  when  mixed  with  as  much  as 
100  per  cent  of  their  own  weight  of  the  coke  dust ;  those  from  the  south- 
ern districts  with  higher  fixed  carbon  do  not  need  so  great  a  dilution. 
Not  only  is  the  texture  made  firmer  by  this  treatment  but  the  density 
is  increased.  Attention  will  be  called  to  the  differences  in  the  prop- 
erties of  the  cokes  in  discussing  the  individual  samples. 


OLIN — THE  COKING  OF  COAL 


Coke  was  made  first  from  Vermilion  County  screenings  such  as 
were  furnished  the  power  plant  of  the  University  of  Illinois.  In  or- 
der to  remove  the  dust  which  may  have  been  more  or  less  weathered, 
the  coal  was  passed  over  a  quarter  inch  screen. 

The  resulting  coke,  shown  in  Fig.  3,  is  extremely  light  and  porous, 
having  a  specific  gravity  of  only  .650.  Its  texture  is  firm,  notwith- 
standing the  low  temperature  at  which  it  was  formed  and  it  has  proved 
its  ability  to  stand  considerable  handling  without  excessive  dusting. 
Moreover,  its  porosity  probably  accounts  in  a  large  measure  for  tie 
success  obtained  in  using  it  in  the  gas  producer  test  described  later, 
since  the  carbon  is  easily  accessible  to  the  blasts  of  hot  air  and  steam. 

The  coke  shown  in  Fig.  4  was  made  from  Saline  County  coal  and 
was  obtained  from  a  run  in  which  the  time  and  temperature  condi- 
tions were  the  same  as  in  that  of  B-10.  It  illustrates  the  superiority  of 
a  coal  from  the  southern  field  for  coking  purposes.  Compared  with 
the  Vermilion  County  sample  its  texture  is  hard  and  firm  and  it  has 
a  density  more  than  6  per  cent  higher  than  the  latter.  It  may  be 
seen  by  referring  to  the  photographs  that  the  cellular  structure  of 
the  Saline  County  sample  is  relatively  close  and  solid,  and  bears  little 
resemblance  to  the  other. 

One  of  the  best  products  obtained  in  this  series  of  experiments  was 
from  a  coal  from  Williamson  County.  This  sample,  B-16,  Fig.  5,  shows 
a  fine  even  grain  and  has  a  density  of  .750,  more  than  15  per  cent  high- 
er than  B-10.  It  has  remarkable  strength,  both  tensile  and  compres- 
sive,  and  stands  rough  handling  without  appreciable  dusting. 

Other  coals  from  Williamson  County  have  shown  the  good  coking 
qualities  which  characterize  the  southern  types.  The  particular  sam- 
ple illustrated  in  Fig.  6  shows  an  uncarbonized  center  but  the  outer 
portion  is  consistently  dense  and  hard  and  has  considerable  strength. 

In  the  course  of  the  work  tests  were  made  of  many  coals  from  other 
localities  as  well  as  from  different  beds  in  the  same  locality.  Included 
in  the  list  are  samples  from  Perry,  Franklin,  Jefferson,  and  Jackson 
Counties,  but  the  cokes  made  from  them  are  so  similar  in  quality  to 
those  already  described  that  they  are  not  separately  discussed. 

TABLE  2. 
COMPOSITION  OF  COKE  FROM  RAW  COALS. 


Sample 

Moisture 

Ash 

Volatile  Matter 

Fixed  Carbon 

S 

Heat 
Value 
B.  t.  u. 

B-10 
B-12 
B-16 
B-19 

1.85 
1.20 
3.25 
2.25 

13.8 
11.9 
12.4 
11.75 

13.20 
10.85 
11.50 
12.30 

71.10 
75.95 

72.85 
73.70 

3.0 
1.6 
1.5 
1.55 

11891 
12520 
12600 
12415 

10 


OLIN — THE  COKING  OF  COAL 


The  effect  of  the  addition  of  a  fine  inert  diluting  medium  to  differ- 
ent types  of  raw  coal  is  seen  in  samples  B-18  and  B-21,  Fig.  7  and 
Fig.  8.  The  former  is  the  product  from  the  heating  of  a  mixture  of 
equal  parts  of  Williamson  County  coal  and  the  coke  dust  described 
on  page  8.  It  is  loose  in  texture  and  crumbles  easily  showing  a  defi- 
ciency in  bonding  material.  On  the  other  hand,  B-21,  made  from  equal 
parts  of  Vermilion  County  coal  and  the  coke  in  question,  is  quite  as 
hard  and  firm  as  the  raw  coal  product  and  considerably  denser.  B-22, 
Fig.  9,  is  from  Vermilion  County  coal  -diluted  with  one-half  its  weight 
of  inert  material  and  while  it  resembles  B-21  it  has  a  lower  specific 
gravity. 

Williamson  County  coal  although  unable  to  cement  itself  firmly 
when  mixed  with  an  equal  weight  of  non-coking  material  nevertheless 
works  successfully  in  a  mixture  of  two  parts  coal  to  one  part  inert 
material.  B-25,  Fig.  10,  is  both  coherent  and  dense  proving  that  the 
dilution  limit  has  at  least  not  been  exceeded  in  applying  this  mixing 
ratio. 

Saline  County  coal  likewise  produces  better  coke  with  the  addition 
of  foreign  material.  B-13,  Fig.  11,  raw  Saline  County  coal  two  parts 
and  coke  dust  one  part,  is  superior  in  every  way  to  the  coke  from  the 
raw  coal  alone. 

The  composition  of  this  series  of  samples  is  given  in  the  following 
table. 

TABLE  3. 
COMPOSITION  OF  COKES  FROM  MIXTURES  OF  COAL  AND  COKE  DUST. 


Sample 

Moisture 

Ash 

Volatile  Matter 

Fixed  Carbon 

3 

Heat 
Value 
B.  t  u. 

B-21 
B-18 
B-22 
B-13 
B-25 

1.35 
1.30 
1.60 
1.40 
1.45 

14.95 
12.9 
14.50 
14.2 
15.4 

13.7 
13.90 
12.70 
15.22 
10.50 

70.0 
71.90 
71.20 
69.18 
72.65 

3.15 
2.50 
2.9 
2.8 
3.0 

11750 
12295 
11825 
12150 
11920 

The  rise  in  the  density  of  the  coke  with  the  addition  of  the  inert 
substance  is  shown  by  the  results  of  the  following  specific  gravity 
measurements. 


OLIN THE  COKING  OP  COAL  I  I 

TABLE  4. 
DENSITIES  OF  COKES. 


Description 

Density 

(B-12 

(unmixed) 

.687 

Saline  County  Coal 

\  B-24 

(raw    %,   dust    %  ) 

.775 

/B-13 

(raw  %,  dust   ^) 

.868 

Williamson  County  Coal 

I  B-16 
(B-25 

(unmixed) 
(raw  %,  dust  ^) 

.750 
.969 

(B-10 

(unmixed) 

.650 

Vermilion  County  Coal 

-(B-22 

(raw  %,   dust   */3) 

.848 

1  B-21 

(rawVz,   dust    V2  ) 

852 

For  purposes  of  comparison  it  is  interesting  to  note  that  B-29,  Fig. 
12,  a  16-hour  Solvay  coke  from  an  Illinois  coal  has  a  density  of  .830 ; 
B-30,  Fig.  13,  a  48-hour  compressed  charge,  .986 ;  while  a  representa- 
tive sample  of  bee-hive  Connellsville  has  a  density  of  about  1.12. 

While  the  methods  described  in  the  foregoing  may  not  be  applied 
directly  on  a  commercial  scale  to  operations  for  making  metallurgical 
coke,  still  it  is  hoped  that  the  results  obtained  may  at  least  help  to 
establish  the  characteristics  of  the  coals  of  the  State  with  regard  to 
their  adaptability  to  this  use  and  to  suggest  methods  and  principles 
on  which  to  work  in  solving  the  problem  of  making  cokes  of  good  qual- 
ity from  such  material.  Unquestionably  they  possess  coking  proper- 
ties to  a  marked  degree  but  need  to  be  treated  differently  from  the 
eastern  coals  with  their  higher  percentages  of  fixed  carbon. 

6.  Gas  Producer  Tests. — Early  in  the  course  of  this  work,  the 
study  of  the  products  resulting  from  the  distillation  of  bituminous 
coals  at  low  temperatures  suggested  the  possibility  of  using  them  as 
fuels  for  the  gas  producer  whereby  it  was  hoped  to  obtain  gases  suffi- 
ciently free  from  tar  to  be  suitable  for  use  in  the  internal  combustion 
engine.  Previous  experiments  had  shown  that  the  moderate  tempera- 
tures of  the  preliminary  heating  period  were  effective  in  expelling  the 
major  part  of  tho  tar-producing  substances  and  that  the  residue,  dis- 
tilled a  second  time  at  high  temperatures,  yielded  gases  remarkably 
free  from  heavy  condensation  products. 

In  order  to  give  the  matter  a  practical  test,  arrangements  were 
made  with  Professor  C.  R.  Richards  of  the  Department  of  Mechanical 
Engineering  of  the  University  of  Illinois  for  the  use  of  the  necessary 
apparatus  of  his  department  and  with  Mr.  A.  P.  Kratz  of  the  Engi- 
neering Experiment  Station  for  his  services  in  conducting  the  trial 


12  OLIN — THE  COKING  OF  COAL 

run.    By  means  of  the  device  already  described  a  quantity  of  coke  was 
prepared  and  it  was  fired  in  the  usual  manner. 

The  fuel  used  in  this  test  was  the  semi-coke  product  obtained  in 
subjecting  Vermilion  County  screenings  from  the  University  power 
plant  to  low  temperature  distillation  (400°C-550°C).  This  test  ma- 
terial, four  or  five  hundred  pounds  in  weight,  consisted  of  pieces  vary- 
ing in  size  from  three-fourths  of  an  inch  to  two  inches  in  diameter, 
but  the  charge  as  fired  contained  some  dust.  It  was  light  and  porous 
and  lay  on  the  fuel  bed  without  showing  much  tendency  to  pack.  The 
following  tables  show  its  composition. 

TABLE  5. 
PROXIMATE  ANALYSIS  OF  PRODUCER  TEST  FUEL. 

Moisture  2.28 
Ash  15.82 
Sulphur  3.13 
Volatile  Matter  18.00 
Fixed  Carbon  63.90 
Calorific  Value  (B.  t.  u.) 11601 

TABLE  6. 
ULTIMATE  ANALYSIS  OF  PRODUCER  TEST  FUEL. 

Carbon  69.86 
Hydrogen  2.76 
Oxygen  5.15 
Nitrogen  (estimated)  1.00 
Sulphur  3.13 
Ash  lo.82 
Water 2.28 

The  producer  used  was  a  Number  3  Otto,  designed  to  operate  on 
anthracite  pea  coal,  with  a  wet  scrubber  attached.  The  latter  was 
merely  a  shell  filled  with  coke  through  which  the  gas,  admitted  at  the 
bottom,  passed  counter  to  a  stream  of  water  flowing  from  the  top. 
Using  anthracite  coal  the  normal  capacity  of  the  producer  was  4500 
cu.  ft.  of  gas  per  hour. 

In  place  of  the  gas  engine  which  under  normal  working  conditions 
draws  the  gas  from  the  scrubber,  a  Schiitte-Koerting  steam  ejector  was 
used.  This  delivered  the  mixture  of  steam  and  gas  to  a  condenser  and 
thence  to  a  Westinghouse  meter  of  the  wet  type  which  had  been  cali- 
brated just  before  the  test  was  made. 

Inasmuch  as  the  supply  of  fuel  was  limited  the  usual  method  of 


OLIN — THE  COKING  OP  COAL  I  3 

starting  and  stopping  was  varied  somewhat.  Before  beginning  the 
experimental  part  of  the  work,  the  producer  was  fired  with  anthracite 
and  thoroughly  warmed  up.  This  fire  was  then  drawn  and  a  new  one 
made  with  a  weighed  amount  of  wood  and  the  fuel  to  be  tested,  and 
the  operation  continued  until  gas  of  a  good  quality  was  given  off,  when 
the  test  was  declared  begun.  During  this  preliminary  period,  as  in 
the  rest  of  the  run,  the  measured  gas  was  sampled  by  means  of  the  con- 
tinuous sampler  which  is  a  part  of  the  installation. 

At  the  close  of  the  test,  the  fuel  bed  was  burned  as  low  as  was 
deemed  practicable,  the  ash  pit  cleaned,  and  the  ash  weighed  and  sam- 
pled. The  residue  on  the  grates  was  then  drawn  out,  quenched, 
weighed,  and  sampled. 

After  the  test  was  started  all  the  coal  put  into  the  producer  was 
weighed.  The  total  fuel  charge  used  in  the  test  then  included  the  coal 
equivalent  of  the  wood  and  coal  used  to  start,  plus  the  coal  fired  dur- 
ing the  test,  minus  the  coal  equivalent  of  the  carbon  in  the  gas  given 
off  before  the  formal  start,  minus  the  coal  equivalent  of  the  residue  in 
the  fuel  bed  at  the  close.  Putting  this  into  a  formula : 

( W3+W5)  14560  +  Wt  X  62000 

=     "  1  T     ™2~  ~~TT 

W  =  Total  weight  of  equivalent  coal  fired  during  test. 

Wi  =  Total  weight  of  equivalent  coal  in  producer  at  start. 

W2  =  Total  weight  of  coal  fired  during  test. 

W3  =  Total  weight  of  carbon  appearing  in  gas  before  starting. 

W4  =  Total  weight  of  hydrogen  appearing  in  gas  before  starting. 

W5  =  Total  weight  of  carbon  within  fuel  bed  at  close  of  test. 

H  =  Heating  value  of  the  coal,  B.  t.  u. 

Since  the  first  sample  contained  practically  no  hydrogen  the  last 
term  in  the  above  formula  becomes  zero. 

Gas  samples  were  drawn  from  a  point  beyond  the  ejector  where  the 
gas  was  under  pressure,  and  were  taken  over  mercury.  Coal  and  ash 
samples  were  taken  in  the  usual  manner. 

Water  fed  into  the  vaporizer  was  weighed  in  a  tank  on  scales.  The 
weight  of  the  overflow  from  the  vaporizer  was  obtained  in  the  same 
manner,  and  the  weight  of  the  water  going  into  the  fuel  bed  from  this 
source  was  the  difference  between  these  two. 

All  temperatures  were  taken  with  mercury  thermometers  with  the 
exception  of  that  of  the  gas  at  the  producer  outlet  which  was  obtained 
by  means  of  a  Hoskins  pyrometer. 


14  OUN — THE  COKING  OF  COAL 

An  attempt  was  made  to  get  tar  samples  just  as  the  gas  left  the 
producer  but  it  was  found  that  the  amount  of  tar  formed  was  not 
appreciable  and  the  sampling  was  discontinued. 

The  Junker  calorimeter  was  used  to  obtain  the  heating  value  of  the 
gas,  about  one  sample  an  hour  being  taken. 

The  form  for  recording  the  results  of  this  test  is  abridged  from 
the  one  given  in  Bulletin*  No.  50  of  the  University  of  Illinois  En- 
gineering Experiment  Station,  where  details  of  methods  of  computa- 
tion may  also  be  found. 

The  firing  sheet  for  this  test  showed  that  the  producer  ran  success- 
fully and  gave  little  trouble.  Because  of  the  small  diameter  of  the 
fuel  bed,  resulting  in  considerable  friction,  the  lightness  of  the  ma- 
terial used,  and  its  slight  tendency  to  coke  and  arch,  the  fuel  above 
the  bed  proper  did  not  feed  down  as  rapidly  as  it  was  burned.  Hence 
it  was  necessary  about  once  an  hour  to  poke  it  down  with  a  slice  bar 
and  in  this  respect  it  probably  required  a  little  more  attention  than  a 
charge  of  anthracite. 

It  may  be  noted,  however,  that  it  was  necessary  to  poke  and  clean 
the  grates  from  the  bottom  but  once  during  the  six  hours  of  the  trial. 
With  so  small  a  producer  this  indicates  a  remarkable  freedom  from 
ash  and  clinker  trouble.  On  cleaning  the  fire  small  pieces  of  clinker 
were  found  in  the  ash,  but  there  was  none  at  all  sticking  to  the  sides, 
where  it  usually  collects.  The  high  grate  efficiency,  98.2  per  cent,  also 
shows  that  the  fires  required  little  attention,  since  poking  and  cleaning 
invariably  force  much  unburned  carbon  out  into  the  ash. 

The  fact  that  the  fire  required  so  little  attention  has  an  added 
significance  in  connection  with  a  producer  having  a  small  fuel  bed, 
such  as  the  one  used  in  this  test.  Usually,  the  inrush  of  air,  when 
the  doors  are  opened  for  cleaning,  dilutes  the  gases  sufficiently  to 
make  them  too  lean  to  burn,  but  with  the  fuel  in  question  less  trouble 
was  experienced  in  this  respect  than  is  usually  the  case  with  anthra- 
cite, for  at  no  time  did  the  pilot  flame  go  out  and  there  was  no  great 
variation  in  the  calorimeter  readings. 

A  study  of  the  temperature  of  the  gas  leaving  the  producer  throws 
considerable  light  on  the  condition  of  the  fuel  bed.  If  the  bed  becomes 
clinkered,  or  if  holes  form  in  the  fire,  air  goes  through  without  coming 
into  intimate  contact  with  the  carbon.  This  chimney  effect  causes  the 


*Tests  of  a  Suction  Gas  Producer.      Garland  and  Kratz.    1912. 


OLIN — THE  COKING  OF  COAL  I  5 

gas  to  burn  at  the  surface  of  the  bed  and  the  temperature  to  rise. 
Sometimes  it  is  very  difficult  to  keep  the  temperature  down  and  clean- 
ing and  poking  have  little  effect.  In  the  case  under  discussion,  how- 
ever, the  temperature  never  rose  above  420 °C  except  during  the  last 
twenty  minutes  of  the  test,  when  the  fire  was  so  low  that  it  was  essen- 
tially a  furnace  and  not  a  producer. 

No  trouble  was  experienced  with  tar.  There  was  little  evidence  of 
its  presence  in  the  fuel  bed,  and  an  attempt  to  get  a  sample  of  it  from 
the  gas  leaving  the  producer  showed  that  it  was  present  in  negligible 
quantities  only.  On  cleaning  the  ejector  at  the  close  of  the  run  a  small 
amount  of  tar  was  noticed  but  most  of  the  deposit  was  of  the  nature  of 
scale.  It  is  to  be  remembered  that  before  going  to  the  ejector  the 
gas  had  first  passed  through  the  scrubber. 

The  efficiencies  (hot  gas  74.4  per  cent  and  cold  gas  64.9  per  cent) 
compare  very  favorably  with  those  obtained  in  using  anthracite  coal  of 
the  same  ash  content. 

Data  and  results  are  given  in  the  following  table. 

TABLE  7. 
RESULTS  OF  GAS  PRODUCER  TRIAL. 

Made  by  A.  P.  Kratz  and  H.  L.  Olin. 

Mechanical  Engineering  Laboratory,  University  of  Illinois. 

Make  of  Producer,  Otto. 

Kind  of  Fuel — Semi-coked  Vermilion  County  Coal. 

Type  of  Producer — Suction  for  Anthracite. 

Duration  of  Trial — hours 6.33 

DIMENSIONS    AND    PROPORTIONS 

Great  area,  sq.  ft 1.666 

Mean  diameter  of  fuel  bed,  ft. 1.545 

Depth  of  fuel  bed,  ft 2.21 

Area  of  fuel  bed,  sq.  ft 1.877 

Approximate  width  of  air  spaces  in  grate,  inches 0.5 

Area  of  air  space,  sq.  ft '. 0.722 

Ratio  of  air  space  to  whole  grate 0.433 

Area  of  discharge  pipe,  sq.  ft 0.165 

Water  heating  surface  in  vaporizer,  sq.  ft 2.7 

AVERAGE  PRESSURES 

Average  corrected  barometer  reading,  inches  mercury 29.52 

Draft  in  ash  pit,  inches  water 0.45 

Suction  at  producer  outlet,  inches  water 0.88 

Pressure  at  meters,  inches  water 3.69 

Absolute  pressure  at  meters,  inches  mercury 29.69 

Vapor  pressure  at  meters,  inches  mercury 1.9 

Dry  gas  pressure  at  meters,  inches  water 27.79 


1 6  OLIN — THE  COKING  OF  COAL 

TABLE  7.    (CONTINUED) 

AVERAGE  TEMPERATURES  (Degrees  Centigrade) 

At  barometer,    28.3 

Of  fire  room,   33.3 

Of  feed  water  entering  vaporizer, 23.4 

Overflow  from  vaporizer, 84.8 

Of  water  entering  scrubber,   14.8 

Of  water  leaving  scrubber,   45.7 

Of  gases  leaving  producer    378.0 

Of  gases  leaving  first  scrubber,  34.5 

Of  gases  entering  meters,   38.2 

Of  gases  entering  meters,  (absolute)    311.2 

FUEL 

Weight  of  wood  used  in  starting,  Ib 9 

Volume  of  gas  given  off  before  start  of  test,  cu.  ft 2238 

Volume  of  standard  gas  given  off  before  start  of  test,  cu.  ft 2010 

Weight  of  equivalent  coal  as  fired,  Ib 381 

Percentage  of  moisture  in  coal   2.28 

Total  weight  of  dry  coal  fired,  Ib 372 

Total  ash  and  refuse,  Ib 37 

Total  weight  of  residual,  Ib 49 

Total  weight  of  combustible,  Ib 280.6 

COMPOSITION  OP  PRODUCER  FUEL 

Fixed  carbon,  per  cent 70.77 

Volatile  matter,  per  cent 18.00 

Moisture,  per  cent  2.28 

Ash,  per  cent   15.82 

Sulphur,  separately  determined,  per  cent 3.13 

ULTIMATE  COMPOSITION  OF  PRODUCER  FUEL 

Carbon,  per  cent   71.50 

Hydrogen,  per  cent 2.82 

Oxygen,  per  cent  5.26 

Nitrogen,  per  cent 1.02 

Sulphur,  per  cent    3.20 

Ash,  per  cent    16.20 

Moisture  in  sample  coal  as  received,  per  cent 2.28 

COMPOSITION  OF  DRY  ASH  AND  REFUSE 

Carbon,  per  cent 14.48 

Earthy  matter,  per  cent 85.52 

COMPOSITION  OF  RESIDUAL  FUEL  ON  GRATE 

Carbon    36.46 

Volatile  matter    7.10 

Moisture    1.18 

Ash   55.30 

FUEL   CONSUMPTION  PER   HOUR 

Dry  coal  per  hour,  Ib 58.8 

Dry  coal  per  sq.  ft.  of  grate  area  per  hr.,  Ib 35.3 

Dry  coal  per  sq.  ft.  of  fuel  bed  per  hr.,  Ib.  . . , 31.3 


OLIN — THE  COKING  OF  COAL  I  J 

TABLE  7.    (CONTINUED) 

CALORIFIC  VALUE  OF  FUEL 
Calorific  value  by  oxygen  calorimeter,  per  Ib.  dry  coal,  B.  t.  u 11601 

WATER 

Total  weight  fed  to  vaporizer,  Ib 440.0 

Total  weight  of  overflow,  Ib 256.0 

Water  actually  evaporated  in  vaporizer,  Ib 184.0 

Weight  of  water  fed  to  producer,  Ib. 

(a)  From  vaporizer    184.0 

(b)  In  air  (estimated)    6.0 

(c)  In  coal 8.7 

Total    199 

Total  weight  of  water  decomposed  as  used  in  calculations,  Ib 91. 

Total  weight  of  moisture  in  gas  leaving  producer,  Ib 108. 

Weight  of  water  decomposed  per  Ib.  of  gas  generated,  Ib 0.0588 

Weight  of  water  decomposed  per  Ib.  of  dry  coal  fired,  Ib 2.42 

Total  weight  of  scrubber  water,  Ib 5880 

GAS 

Calorific  value  per  cu.  ft.    of  standard  gas  from  calorimeter,  B.  t.  u. 

(high  value) .'  121 

Specific  weight  of  standard  gas,  Ib.  per  cu.  ft 0.0670 

Specific  heat  of  dry  gas  leaving  producer  (estimated)    0.260 

Total  volume  of  gas  from  meters,  cu.  ft 26927 

Total  volume  of  standard  gas  at  16.5°C.  and  30  in.,  cu.  ft 23150 

Volume  of  standard  gas  per  hr.  cu.  ft 3660 

Volume  of  standard  gas  per  Ib.  of  dry  coal  cu.  ft 62.3 

Total  weight  of  standard  gas,  Ib 1552. 

Weight  of  standard  gas  per  Ib.  of  dry  coal,  Ib 4.17 

COMPOSITION  OF  GAS  BY  VOLUME 

Carbon  dioxide,   CO2   4.15 

Carbon  monoxide,  CO  21.10 

Oxygen,  O2 0.30 

Hydrogen,  H2  (estimated  from  calorific  value)    11.80 

Marsh  gas,  CH4 1.50 

Nitrogen,  N2  by  difference 61.00 

COMPOSITION  OF  GAS  BY  WEIGHT 

Carbon  dioxide,  CO2    7.19 

Carbon  monoxide,  CO 23.17 

Oxygen,  O3 0.38 

Hydrogen,  H3    0.93 

Marsh  gas,  CH4 0.96 

Nitrogen,  N2  by  difference 67.37 

EFFICIENCY 

Grate  efficiency,  per  cent  . . : 98.2 

Hot  gas  efficiency,  based  on  high  heating  value,  per  cent 74.4 

Cold  gas  efficiency,  based  on  low  heating  value,  per  cent 64.9 


I  8  OLIN — THE  COKING  OF  COAL 

7.  Adaptation  of  the  Coke  to  Domestic  Appliances. — A  limited 
amount  of  the  coke  was  available  for  testing  its  adaptability  to  house- 
heating  purposes.    The  ordinary  household  appliance  is  especially  well 
adapted  for  distilling  off  the  hydrocarbons  of  coal  and  sending  them 
into  the  air  unburned  or  partly  burned  and  accompanied  by  large 
volumes  of  smoke. 

In  the  coke  product  here  described  the  heavy  hydrocarbons  have 
been  removed.  The  coke  itself,  therefore,  is  clean  both  in  handling 
and  in  burning.  However,  there  remains  approximately  20  per  cent  of 
volatile  matter  which  enters  into  the  process  of  combustion  after  the 
coke  has  attained  a  temperature  at  or  beyond  the  point  to  which  it  had 
been  subjected  in  the  coking  process.  These  conditions  result  in  a  free 
burning  substance  yet  one  whose  combustible  constituents  may  not 
produce  smoke  in  burning. 

An  open  grate  was  selected  as  furnishing  the  best  opportunity  for 
observing  the  behavior  of  the  material.  The  results  are  summed  up 
as  follows:  the  coke  ignites  readily,  it  retains  its  shape  through  the 
process  of  combustion,  a  bed  of  glowing  coals  quickly  results,  the  very 
indifferent  provision  for  draft  as  found  in  an  open  grate  is  sufficient 
for  keeping  the  combustion  lively,  there  is  no  smoke  produced,  and 
fire  is  retained  over  a  long  period  of  time,  because  the  interior  of  the 
larger  pieces  holds  the  fire  and  continues  the  combustion  until  all  of 
the  carbonaceous  matter  is  consumed.  While  the  temperature  com- 
monly attained  by  a  grate  fire  would  not  furnish  positive  evidence  as 
to  the  formation  of  clinker,  the  indications  so  far  as  they  went,  were 
altogether  favorable.  A  small  amount  of  coke  was  tested  by  burning 
in  a  hot  air  furnace.  Not  enough  material  was  at  hand  for  a  complete 
test,  but  so  far  as  observations  could  be  made,  it  was  as  favorable  as  the 
test  in  the  open  grate. 

8.  The  Sources  and  Uses  of  Coal  Tar. — The  installation  of  the  first 
American  by-product  recovery  coke  plant  in  1893  marks  the  beginning 
of  a  notable  rise  in  the  production  and  use  of  coal  tar  in  this  country. 

Previous  to  that  time  the  isolated  illuminating-gas  plant  was  the 
only  source  of  supply  and,  indeed,  in  the  smaller  places  at  least,  the 
tar  was  looked  upon  as  a  troublesome  waste  product  rather  than  as  a 
thing  of  value. 

For  making  metallurgical  coke,  types  of  beehive  ovens  of  varying 
degrees  of  efficiency  were  employed  and  these,  of  course,  allowed  the 
volatile  constituents  of  the  coal,  both  gaseous  and  liquid,  to  be  wasted. 


OLIN — THE  COKING  OP  COAL  19 

In  1912,  not  twenty  years  after  the  introduction  of  the  new  type 
of  oven,  165,000,000  gallons  of  tar  were  produced  in  the  United  States, 
and  two  thirds  of  this  quantity,  according  to  Perry,*  came  from  the 
by-product  coke  plant.  With  the  steady  increase  in  by-product  oven 
construction  the  tar  refining  industry  will  assume  a  proportionate  im- 
portance. 

Of  the  various  fractions  obtained  in  distilling  the  crude  tar  the 
most  important  are ; — benzol  and  its  homologues,  used  in  the  color  in- 
dustry and  as  paint  and  fat  solvents;  the  carbolic  oils,  much  in  de- 
mand for  disinfectants  of  various  kinds ;  and  the  creosote  and  anthra- 
cene oils,  of  great  importance  in  the  preserving  of  wood.  The  pitch 
residue  is  used  in  roofing,  paving,  and  road-building,  but  in  these  fields 
it  meets  strong  competition  with  the  mineral  bitumens  and  conse- 
quently does  not  find  so  ready  a  market  as  the  other  constituents 
named.  But  pitch  makes  up  the  greatest  part  of  the  crude  tar  aggre- 
gate, being  in  most  cases  considerably  more  than  half.  The  bulk  of 
the  raw  material  therefore,  is  in  the  form  of  high  temperature  con- 
densation products  and  free  carbon  of  relatively  small  value,  while  the 
supply  of  the  lighter  fractions  is  insufficient  to  meet  the  demand.  This 
is  especially  true  of  those  compounds  of  the  tar  which  have  bacteri- 
cidal properties.  With  the  rapid  depletion  of  the  forests  and  the  cut- 
ting off  of  lumber  supplies,  wood  preserving  treatment  has  become  im- 
perative in  many  industries — particularly  that  of  the  railroads — and 
the  lack  of  available  material  for  this  process  is  causing  much  concern. 
American  supplies  are  inadequate  for  home  consumption  and  nearly 
45,000,000  gallons  of  creosote  oils  were  imported  from  Europe  in  1911. 
Any  modification  of  the  coking  process,  therefore,  that  will  increase 
the  yield  of  the  light  tars  by  preventing  their  condensation  to  com- 
pounds of  high  molecular  weight  will  effect  a  considerable  economy. 
Considerations  of  this  kind  have  lent  interest  to  the  study  of  the  tars 
obtained  in  the  course  of  these  experiments,  in  which  temperatures 
were  kept  much  below  those  of  the  gas  retort  and  the  commercial  coke 
oven. 

9.  Methods  for  Testing  and  Analyzing  Tars. — Of  the  methods  pro- 
posed and  outlined  for  testing  tar,  perhaps  the  best  are  those  published 
by  S.  R.  Church  in  a  paper  on  "  Methods  for  Testing  Coal  Tar  and 
Refined  Tars,  Oils  and  Pitches  Derived  Therefrom,  "f  These  tests,  as 


*Eighth  Int.  Cong,  of  App.  Chem.,  10,  233. 

fThe  Gas  Age,  32,  103.     Jour,  of  Ind.  and  Eng.  Chem.,  3,  227. 


2O  OLIN — THE  COKING  OP  COAL 

he  says  in  the  introduction,  were  not  put  forward  as  methods  for  the 
scientific  examination  of,  or  research  into,  the  products  of  coal  tar,  but 
rather  as  an  attempt,  in  cooperation  with  other  chemists  of  the  com- 
pany with  which  he  was  connected,  to  revise  and  standardize  the  every- 
day tests  applied  to  the  raw  materials  and  products  of  the  American 
tar  distiller. 

In  this  article  he  takes  up  the  determination  of  water,  free  carbon, 
fixed  carbon,  and  ash,  and  the  measuring  of  the  specific  gravity  and 
viscosity  of  the  raw  tar,  distilled  tars,  and  pitch.  He  then  outlines  the 
chemical  investigation  of  the  light  oils,  carbolic  oils,  benzols  and  creo- 
sotes, including  the  estimation  of  napthalene.  In  a  later  paper1  he 
gives  some  supplementary  methods. 

Prevost  Hubbard's  "Methods  for  the  Examination  of  Bituminous 
Road  Materials '  '2  approaches  the  matter  solely  from  the  standpoint  of 
the  road-builder,  and  takes  up  the  physical  tests  necessary  to  deter- 
mine the  fitness  of  the  material  for. this  special  purpose.  In  its  field 
it  is,  unquestionably,  authoritative. 

Among  the  publications  devoted  particularly  to  methods  for  test- 
ing wood  preservatives  may  be  mentioned  those  of  the  American  Rail- 
way Engineering  Association,3  the  National  Electric  Light  Associa- 
tion,4 and  the  Forest  Service  of  the  Department  of  Agriculture.5 

In  addition  to  the  foregoing,  the  following  works  take  up  to  a 
greater  or  less  extent  the  subject  of  coal  tar  analysis: 

Sadtler,  Industrial  Organic  Chemistry,  3rd.  ed.  J.  B.  Lippin- 
cott  Co. 

Rogers  'and  Aubert,  Industrial  Chemistry,  1913,  Van  Nostrand  Co. 

Lunge,  Coal  Tar  and  Ammonia,  4th  ed.  1909.    Van  Nostrand  Co. 

Allen,  Commercial  Organic  Analysis.  Vol.  II,  part  2,  3rd.  ed.  1909. 
Blakiston's  Son  and  Co.,  Philadelphia. 

Mulliken,  Identification  of  Pure  Organic  Compounds.  1904.  Wiley 
and  Sons. 

10.  Properties  of  Tar  Products  From  Low  Temperature  Coal 
Distillation. — The  tar  used  in  this  investigation  was  the  product  ob- 
tained in  a  separate  series  of  runs  made  with  Vermilion  County  coal. 


.  of  Ind.  and  Eng.  Chem.,  5,  195. 
2U.  S.  Dept.  of  Agriculture,  Office  of  Public  Roads,  Bulletin  38,  1911. 
3Bulletin  65,   American  Railway  Eng.  Assoc. 

4Report  of  Committee  on  Preservative  Treatment  of  Poles  and  Crossarms,  1911. 
BDean  and  Bateman,  Circular  112,   "Analysis  and  Grading  of  Creosotes." 


FIG.  3.  B-10.  VERMILION  COUNTY  COKE 


FIG.  4.  B-12.  SALINE  COUNTY  COKE 


FIG.  5.    B-16.    WILLIAMSON  COUNTY  COKE 


FIG.  6.    B-19,    WILLIAMSON  COUNTY  WASHED  NUT  COKE 


FIG.  7.     B-18.     COKE  FROM  WILLIAMSON  COUNTY  COAL  MIXED  WITH  COKE  DUST 


FIG.  8.    B-21.    COKE  FROM  EQUAL  PARTS  OF  VERMILION  COUNTY  COAL 
AND  COKE  DUST 


FIG.  9.     B-22.     COKE  FROM  VERMILION  COUNTY  COAL  AND  COKE  DUST 


FIG.  10.    B-25.     COKE  FROM  WILLIAMSON  COUNTY  COAL  AND  COKE  DUST 


FIG.  11.     B-13.     COKE  FROM  SALINE  COUNTY  COAL  AND  COKE  DUST 


FIG.  12.     B-29.     16-HOUR  SOLVAY   COKE 


13.     B-30.     48-HOUR  COMPRESSED  SOLVAY  COKE 


OLIN — THE  COKING  OF  COAL  2  I 

To  prevent  oxidation  and  evaporation  the  tar  was  protected  as  soon 
as  formed  with  a  water  seal,  and  kept  in  air-tight  cans  until  used  for 
analysis. 

The  tar  is  fluid  at  temperatures  considerably  below  room  condi- 
tions. In  appearance  it  is  black  to  rich  brown  with  varying  thickness 
of  layer,  and  it  possesses  an  exceedingly  disagreeable  odor  even  when 
judged  by  coal  tar  standards. 

The  specific  gravity  measured  with  a  pyknometer  at  20°  was  1.069. 
Its  low  density  makes  its  separation  from  water  by  gravity  somewhat 
difficult  and  there  is  a  tendency,  moreover,  for  high  fractions  to  float 
on  the  surface  of  the  water.  Its  viscosity  is  low  and  in  this  respect  it 
resembles  a  mineral  oil  rather  than  a  high  temperature  coal  tar. 

The  percentage  of  free  carbon,  or  more  accurately,  of  substances 
insoluble  in  toluene  and  benzene,  was  found  by  treating  a  compara- 
tively large  sample  of  the  dry  tar,  (about  36  grams)  with  toluene,  and 
heating  the  mixture  on  the  steam  bath.  The  solution  was  decanted 
through  two  S  and  S  filter  cones  (33  mm.  and  26  mm.)  one  within 
the  other.  After  three  treatments  the  whole  mass  was  transferred  to 
the  cones  and  extracted  with  benzene  in  a  Soxhlet  apparatus  until  the 
filtrate  was  colorless.  Check  results  showed  a  free  carbon  content  of 
1.35  per  cent. 

Fixed  or  combined  carbon  may  be  determined  by  a  method  based  on 
the  report  of  the  Committee  on  Coal  Analysis  of  the  American  Chem- 
ical Society.*  The  cracking  of  an  oil  or  tar  is,  however,  so  closely  de- 
pendent upon  time,  temperature,  and  pressure  conditions  that  a  sim- 
ple laboratory  test  of  the  kind  outlined  by  the  Society  would  have  little 
significance. 

11.  Distillation  of  Tar. — In  order  to  dry  the  tar  a  preliminary 
distillation  125°  was  made  and  the  light  oil  runnings  after  being 
separated  from  the  water  were  returned  to  the  retort.  The  apparatus 
used  was  an  ordinary  Jena  distilling  flask  attached  to  a  Liebig  con- 
denser. 

In  the  earlier  attempts  to  make  this  separation  much  trouble  was 
caused  by  the  tendency  of  the  water  in  the  crude  material  to  produce 
a  succession  of  "bumpings."  These  explosions  were  often  so  sud- 
den and  violent  as  to  throw  a  considerable  part  of  the  charge  out  of 
the  retort.  This  annoying  feature  was  prevented,  however,  by  run- 
ning a  slow  stream  of  air  through  a  tube  extending  nearly  to  the  bot- 
tom of  the  vessel,  and  later,  in  order  to  prevent  oxidation  which  seemed 


*Jour.   Am.   Chem.   Soc.,   21,   1116. 


22  OLIN — THE  COKING  OF  COAL 

to  take  place  at  the  higher  temperatures  under  these  conditions,  carbon 
dioxide,  which  had  been  previously  washed  and  dried,  was  substituted. 
This  method  was  used  in  all  subsequent  distillations  of  the  crude,  wet 
tar  and  served  the  double  purpose  of  providing  an  inert  atmosphere 
in  which  to  carry  on  the  heating  of  the  substances  making  up  the  ma- 
terial, many  of  which  show  remarkable  chemical  activity,  and  of  mak- 
ing the  boiling  proceed  smoothly  and  quietly.  It  is  to  be  noted,  how- 
ever, that  the  current  of  gas  sent  through  the  apparatus  carries  over 
with  it  a  considerable  quantity  of  material  whose  boiling  point  is  at  a 
temperature  above  that  maintained  in  the  retort.  In  redistilling  the 
dry  tar  to  fractionate  the  sample  this  precautionary  measure  was  un- 
necessary, and  therefore  was  not  taken. 

The  escape  of  the  first  light  oil  runnings  was  prevented  by  sur- 
rounding the  receiving  vessel  with  a  freezing  mixture.  To  condense 
the  heavier  part  of  the  second  fraction,  only  the  inner  tube  of  the  con- 
denser was  used  so  that  heat  might  be  applied  to  facilitate  the  flow  of 
the  viscous  fluid. 

To  insure  greater  accuracy  a  subsequent  redistillation  of  the  light 
oil  fraction  was  made  with  the  use  of  a  Lebel-Henninger  tube,  with  the 
thermometer  so  adjusted  that  the  top  of  the  bulb  was  level  with  the 
side  neck.  The  Liebig  condenser  was  used  as  before.  With  this  ap- 
paratus it  was  possible  to  secure  fractions  with  sharply  defined  boiling 
points,  an  important  prerequisite  to  identifying  individual  com- 
pounds. 

TABLE  8. 
RESULTS  OF  PRELIMINARY  DISTILLATION  OF  TAR. 


Fraction 

Temperature  Range 

Percentage 

Light  oil 
Heavy  oil 
Pitch 

below  210°  0 
210°-325° 
above  325° 

17,2 
52.7 
30.1 

12.  Examination  of  Light  Oil. — The  low  boiling  fraction  purified 
as  indicated  above  is  a  clear  amber  colored  liquid  with  a  disagreeable 
odor.  It  is  very  susceptible  to  the  action  of  light  and  air  and  finally 
turns  dark  red  even  when  sealed  iri  an  atmosphere  of  carbon  dioxide. 

The  separation  and  identification  of  all  the  individual  constituents 
of  a  substance  like  coal  tar  is  a  great  task.  Lunge,  in  his  work  ' '  Coal 
Tar  and  Ammonia"  has  described  more  than  two  hundred  distinct 
compounds  which  occur  in  tars  of  different  qualities  and  his  list  is 
probably  not  complete.  We  are  concerned  in  this  work  merely  with  a 


OLIN — THE  COKING  OF  COAL  23 

few  of  the  most  important  substances  which  are  of  interest  because  of 
their  practical  value  and  not  with  those  which  are  of  interest  from  the 
scientific  standpoint  only. 

The  phenols  and  other  acid  substances  of  the  light  oil  were  sep- 
arated from  the  neutral  and  basic  constituents  by  shaking  the  fraction 
in  a  separatory  funnel  with  half  its  volume  of  10  per  cent  caustic  soda 
solution.  After  this  treatment  had  been  repeated  until  no  further  re- 
duction in  volume  of  the  residue  took  place,  this  caustic  solution  was 
drawn  off  and  acidified  with  sulphuric  acid  and  the  whole  extracted 
with  ether.  The  ether  extract,  when  evaporated  down,  yielded  crude 
phenol  and  its  homologues. 

The  amines  were  removed  from  the  oily  residue  after  the  phenol 
extraction  by  shaking  it  with  dilute  sulphuric  acid,  of  sp.  gr.  1.15, 
with  warming.  The  solution  was  separated  as  before,  neutralized  with 
caustic  soda,  and  the  bases  extracted  with  ether. 

The  method  for  separating  paraffins  and  benzenes  is  based  upon 
the  familiar  principle  that  the  hydrocarbons  of  the  paraffin  series  are 
practically  inert  toward  sulphuric  acid,  while  those  of  the  aromatic 
series  react  with  comparative  ease,  forming  sulphonic  acids,  in  which 
sulpho  groups  replace  hydrogen  of  the  benzene  ring.  These  acids  are 
very  soluble  in  water  and  are  therefore  easily  separated  from  the  in- 
soluble oily  paraffin  residues. 

The  process  used  was  that  adopted  by  the  Forest  Products  Labor- 
atory.* Ten  cubic  centimeters  of  the  fraction  to  be  tested  were  meas- 
ured into  a  Babcock  milk  bottle.  To  this  was  added  40  cc.  of  37  N 
sulphuric  acid  (made  by  adding  the  calculated  amount  of  fuming  sul- 
phuric acid  to  the  ordinary  acid,  sp.  gr.  1.84)  10  cc.  at  a  time.  The 
mixture  after  being  kept  at  100°  C  for  an  hour  was  cooled  and  then 
whirled  for  five  minutes  in  a  Babcock  separator.  The  volume  of  the 
unsulphonated  or  paraffin  residue  was  read  off  directly.  Equally  good 
results  are  obtained,  however,  by  pouring  the  mixture  into  a  large 
volume  of  water  and  separating  by  means  of  the  funnel. 

As  a  step  toward  identifying  those  constituents  which  do  not  react 
with  acids  and  bases,  a  sample  of  the  oil  from  which  the  phenols  and 
pyridines  had  been  removed  but  which  had  not  been  sulphonated,  was 
subjected  to  a  second  redistillation,  with  the  measurement  of  the  vol- 
umes going  over  between  comparatively  narrow  limits  of  temperature. 

A  summary  of  the-  results  obtained  from  the  various  tests  and 
analyses  follows : 


*Bateman,  E.  Modification  of  the  Sulphonation  Test  for  Cresote.     Forest  Service,  Circu- 
lar  191,  U.   S.   Dept.  of  Agriculture. 


OLIN THE  COKING  OF  COAL 


TABLE  9. 
LIGHT  OIL  FRACTION  (TO  210°C). 

Specific  gravity  .966 


Percentage  on  Basis  of 

Percentage  on  Basis  of 

Crude  Tar 

Light  Oil  Fraction 

Light  oil   fraction 

17.2 

100  0 

Phenols  (and  other  acid  substances 

5.7 

33  0 

Amines   (and  other  bases) 

0.9 

5  3 

Paraffins 

3.12 

18.1 

The  results  of  the  refractionation  of  the  light  oil  from  which  the 
acids  and  bases  had  been  removed  are  given  in  the  following  table : 

TABLE  10. 
DISTRIBUTION  OF  NEUTRAL  SUBSTANCES  IN  LIGHT  OIL. 


Fraction 

Percentage  on  Basis  of 
Light  Oil  Fraction 

Percentage  on   Basis  of 
Crude  Tar 

20°-75°  low  boiling  bodies 
75°-95°   crude  benzol    (90%) 
95°-125°   crude  toluol 
125°-170°    crude  solvent  naptha 
170°-200°    crude  heavy   naptha 
200°-210°   crude  heavy  naptha 

5.26 
2.10 
7.36 
26.30 
14.73 
7.30 

.25 
.38 
1.33 

4.77 
2.67 
1.32 

The  classification  as  made  in  Table  10  is  based  on  the  outline  for 
the  examination  of  light  oil  as  given  by  F.  E.  Dodge  in  his  article  on 
' '  Coal  Tar  and  Its  Distillation  Products. '  '*  It  is  understood  that  this 
is  a  generalization  only,  and  that  it  shows  composition  by  classes  of 
compounds  rather  than  by  individuals.  However,  since  the  different 
homologues  of  a  class  within  rather  close  limits  of  the  boiling  point 
usually  differ  little  in  character,  a  fair  idea  of  the  composition  of  the 
mixture  may  be  gained  without  further  separation. 

Fraction  No.  1,  besides  some  benzene,  contains  also  pentanes  and 
hexanes  of  the  paraffin  series,  ranging  in  boiling  point  from  31°  C  to 
64°  C.  No.  2  includes  some  of  the  heptanes  boiling  in  the  nineties; 
No.  3,  according  to  tables  complied  from  dataf  obtained  by  distilling 
known  mixtures,  consists  of  benzene  and  toluene,  the  latter  predom- 
inating, while  fraction  No.  4  includes  the  xylenes  boiling  from  138°  C 
to  143°  C,  with  perhaps  some  mesitylene,  b.p.  164 °C.  Likewise  the 
part  reported  as  phenols  contains  besides,  one  or  all  of  the  three  cre- 
sols,  although  the  close  range  of  boiling  points  (190°,  201°,  and  202°) 
made  a  quantitative  fractionation  of  the  crude  extract  impracticable. 

industrial  Chemistry.     Rogers  and  Aubert,   1912.  p.  492. 

tG.   E.   Davis.   Industrial   Chemistry   Rogers   and   Aubert.  p.   499. 


OLIN — THE  COKING  OF  COAL  25 

Finally,  the  rapid  darkening  of  both  the  neutral  and  the  active 
fractions  on  even  short  time  exposures  to  air  points  to  the  presence  of 
various  unsaturated  substances,  difficult  to  isolate  and  probably  of  no 
great  practical  importance. 

13.  Examination  of  Heavy  Oil  Fraction,  210° C  to  325° C.— The 
heavy  oil  obtained  from  the  first  distillation  to  which  was  added  the 
residue  boiling  above  210°,  from  the  redistillation  of  the  light  oil,  is  a 
thick  viscous  liquid  of  a  rich  brown  color.  After  standing  for  a  time 
a  non-crystalline  sediment  is  formed. 

Tar  acids  were  determined  by  the  methods  used  in  the  examination 
of  the  light  oils  except  that  after  the  addition  of  the  caustic  soda  it 
was  necessary  to  warm  the  mixture  in  order  to  facilitate  the  separa- 
tion, while  the  paraffin  and  aromatic  content  of  substances  was  found 
by  sulphonation  as  before.  Likewise  a  sample  from  which  the  acid 
constituents  had  been  removed  was  ref  ractionated  and  the  volumes  of 
distillate  given  off  between  close  temperature  limits  were  noted. 

The  napthalene  content  was  determined  by  cooling,  with  a  freezing 
mixture,  the  heavy  oil  sample  from  which  the  acids  had  been  extracted, 
in  order  to  crystallize  out  any  of  this  substance  which  might  be  pres- 
ent. The  test  gave  zero  results ;  the  conclusion  is  that  no  napthalene 
was  present.  This  result  is  confirmed  by  observations  made  when  the 
original  tar  was  distilled  from  the  coal,  for  at  no  time  did  the  tar  con- 
denser become  clogged  as  it  would  if  napthalene  were  going  over  even 
in  small  quantities,  nor  did  the  pungent  odor  of  its  vapors  ever  become 
noticeable. 

The  method  for  the  quantitative  assay  of  anthracene  as  given  by 
Allen*  was  used  for  this  material.  The  sample,  dissolved  in  boiling 
glacial  acetic  acid,  was  treated  with  chromic  acid  slowly  dropped 
through  a  reflux  condenser  to  oxidize  any  anthracene  present  to  an- 
thraquinone.  The  results  showed  that  the  amount  present  was  neg- 
ligible. 

TABLE  11. 

COMPOSITION  OF  HEAVY  OIL    (210°C-325°C). 

Specific  gravity  1.032 


Fraction 

Percentage  on  Basis  of 
Crude  Tar 

Percentage  on  Basis  of 
Heavy  Oil  Fraction 

Heavy   oil   fraction 
Tar  acids 
Paraffins 
Napthalene 
Anthracene 

52.7 
22.2 
6.2 
.0 
.0 

100.0 
42.13 
32.66 
.0 
.0 

*  Commercial  Organic  Analysis.     Vol.  II,  part  2,  p.   229. 


26  OLIN — THE  COKING  OF  COAL 

Distillation  of  the  acid  free  samples  gave  the  following  results. 

TABLE  12. 
DISTRIBUTION  OF  NEUTRAL  SUBSTANCES  IN  HEAVY  OIL. 


Fraction 

Percentage  on  Basis  of 
Crude  Tar 

Percentage  on  Basis  of 
Heavy  Oil  Fraction 

210°   to  250° 
250°   to  270° 
270°   to  pitch 

2.87 
13.55 
11.53 

10.3 

48.5 
41.2 

In  attempting  to  identify  the  various  substances  of  the  heavy  oil 
fraction  the  worker  finds  the  problem  even  more  difficult  than  in  the 
case  of  the  light  oil  because  the  higher  boiling  points  and  molecular 
weights  of  the  compounds  make  them  more  difficult  to  separate.  A 
partial  purification  of  the  acid  bearing  extract  of  this  part  of  the  tar 
showed  by  the  boiling  points  that  a  high  percentage  of  creosols  was 
present.  The  higher  boiling  members  were  not  identified.  It  is  pos- 
sible that  they  are  polyhydric  phenols,  such  as  Lewes  mentions  as  be- 
ing present  in  the  tar  from  coalite  and  which  he  says  form  resinous 
masses  difficult  to  investigate. 

Fraction  No.  2  is  the  neutral  part  of  the  cut  in  tar  distilling  known 
as  creosote  oils.  Emmet  and  Reingruber*  say  of  this  class  of  substances 
that  after  removing  basic,  oxygenated,  and  crystallizable  bodies,  there 
remain  several  isomeric  dimethylnapthalenes,  the  separation  of  which 
has  proved  unmanageable,  and  which  constitute  the  major  portion  of 
the  fraction. 

14.  Pitch. — The  residuum  from  the  original  distillation  of  the 
crude  tar  is  a  hard,  black  substance,  rather  brittle,  breaking  with  a 
bright  fracture.  As  indicated  by  the  table  of  its  properties  it  is  a  hard 
pitch,  as  contrasted  with  soft  pitch  having  a  melting  point  of  about 
75°  C. 

TABLE  13. 
PITCH  FRACTION  (ABOVE  325°  C). 

Per  cent  on  basis  of  crude  tar                      30.1 

Melting  point  110°  C 

Specific  gravity  1.27 
Free  carbon 


'Annalen  211,  365. 


OLIN — THE  COKING  OF  COAL  2  7 

15.  Oxygen  Absorbing  Power  of  Tar. — In  the  publication  of  the 
results  of  the  preliminary  studies  of  low-temperature  tar,*  attention 
was  called  to  the  fact  that  both  the  light  and  the  heavy  fractions  were 
readily  oxidizable  and  the  question  was  raised  whether  these  oils  might 
not  serve  as  drying  bodies  or  paint  vehicles  by  forming  coatings  or 
films  on  oxidation.  In  an  attempt  to  approximate  a  quantitative  meas- 
urement of  this  capacity  for  absorbing  oxygen,  a  series  of  iodine  ab- 
sorption determinations  was  made,  with  rather  variable  results. 

Further  investigations  of  the  kind  have  proved  what  was  conceded 
as  a  probability  at  the  time,  that  other  reactions  than  those  of  simple 
saturation  take  place,  chief  among  which  is  substitution  with  the 
formation  of  hydriodie  acid.  While  fairly  consistent  results  have  been 
obtained  in  the  supplementary  work  under  strictly  standard,  condi- 
tions, slight  changes  in  the  concentration  of  the  iodine  solution,  in  the 
time  of  digestion  and  particularly  in  the  temperatures  of  the  reacting 
substances  so  varied  the  values  found  that  the  method  is  deemed  un- 
reliable. Bromine  is  even  more  uncertain.  Among  the  substances 
present  in  the  tar  from  which  hydrogen  is  easily  displaced  by  the  halo- 
gens are  the  phenols,  the  reaction  taking  place  almost  immediately 
even  in  the  cold. 

The  only  reliable  criterion  of  its  value  as  a  paint  drier  is  perhaps 
the  actual  test  of  its  behavior  when  exposed  to  air.  The  light  oil  frac- 
tion forms  a  thin  film  when  spread  on  a  glass  plate  inclined  to  45 
degrees.  Using  good  linseed  oil  as  a  standard  for  reference,  it  is  found 
that  the  tar  oil  films  are  decidedly  thinner,  i.e.,  the  oil  flows  more  be- 
fore thickening,  and  that  the  time  of  maximum  drying  is  from  two  to 
three  times  that  observed  in  the  case  of  the  linseed  oil. 

III.     APPENDIX  OF  SUPPLEMENTARY  EESULTS. 

At  the  request  of  S.  R.  Church,  head  of  the  Research  Department 
of  the  Barrett  Manufacturing  Company  of  New  York,  a  small  sample 
of  the  crude  tar  remaining  after  the  conclusion  of  the  work  described, 
was  sent  to  the  New  York  Laboratories  for  examination.  Mr.  Church, 
in  a  communication  commenting  on  it  briefly,  says,  "This  tar  in  its 
characteristics,  resembles  somewhat  the  Scotch  blast  furnace  tars  al- 
though it  is  higher  in  tar  acid  content  than  the  Scotch  tars,  and  appar- 
ently not  quite  so  high  in  paraffin-like  bodies.  The  most  interesting 
feature  to  us  is  its  exceptionally  high  content  of  oxygenized  compounds 
of  phenoloid  character. ' ' 

*Parr  and  Olin.     Bulletin  No.   60,   University  of  Illinois  Eng.   Exp.   Sta.  p.    13. 


28  OLIN — THE  COKING  OF  COAL 

' '  Should  tar  of  this  nature  become  a  commercial  product,  it  would 
undoubtedly  have  a  certain  value  to  the  tar  distillers  although  it 
would,  of  course,  have  to  be  handled  in  an  entirely  different  manner 
from  the  ordinary  coal  tars. ' ' 

The  outline  of  his  results  is  given  in  the  following  table. 

TABLE  14. 

TESTS  OF  TAR  DERIVED  FROM  THE  DISTILLATION  OF  COAL 
FROM  VERMILION  Co.,  ILLINOIS.    (S.  R.  CHURCH.) 

Water,  per  cent  21.7 

Tests  on  Dry  Tar: 

Specific  gravity  at  15.5° C  1.072 

Free  carbon,  per  cent  1.3 

Light  Oil  (to  210°)  per  cent  by  vol.  15.2 

Heavy  Oil  (to  pitch)  per  cent  by  vol.  40.2 

Light   Oil: 

Tar  acids,  per  cent 30.0 

Sulphonation  residue,  per  cent  15.0 

Heavy  Oil: 

Standard  retort  distillation: 

Total  per  cent  to  170 °C  0.5 

200°  2.0 

210°  6.6 

235°  33.6 

270°  61.0 

315°  65.8 

355°  94.9 

Tar  acids  in  total  distillation  50.0 
Sulphonation  residues  on  fractions             4  to  5  per  cent 
Pitch 

Melting  point,  76  °0 

Free  carbon,  per  cent  9.0 


Of  equal  interest  is  the  supplementary  report  furnished  by  Mr.  E. 
B.  Fulks  of  the  American  Creosoting  Company  of  Louisville,  Ken- 
tucky, who  visited  the  laboratory  early  in  the  year  1913  and  obtained 
a  sample  of  a  tar  similar  to  the  one  that  has  been  discussed.  He  writes : 
' '  This  tar  is  quite  different  from  ordinary  coal  tar,  in  that  it  is  thin- 
ner, has  a  lower  specific  gravity  and  much  smaller  percentage  of  pitch. 
The  principal  difference  however,  is  in  the  high  percentage  of  tar  acids 
and  in  the  presence  of  considerable  quantities  of  paraffinoid  bodies. 
These  differences  probably  would  make  it  necessary  to  work  this  tar 
somewhat  differently  from  the  method  employed  for  ordinary  tars  but 
undoubtedly  it  would  have  considerable  commercial  value." 

"The  quantity  at  our  disposal  was  so  small  that  we  were  unable 
to  separate  an  amount  large  enough  to  test  the  preservative  qualities 
of  that  proportion  which  would  be  used  for  this  purpose.  Apparently, 
however,  this  tar  would  produce  from  30  to  40  per  cent  of  oil  of  fair 
preservative  value.  The  high  percentage  of  tar  acids  would  make  it  a 


OLIN THE  COKING  OF  COAL  2  9 

valuable  source  of  material  for  the  manufacture  of  antiseptic  solutions, 
sheep  dip,  etc.  The  pitch  contains  a  small  proportion  of  free  carbon 
and  probably  could  be  used  for  roofing  purposes  and  paving  filler." 

The  report  of  his  analysis  is  given  in  the  following  table : 

TABLE  15. 

OIL  FROM  Low  TEMPERATURE  COKING  EXPERIMENTS 
UNIVERSITY  OF  ILLINOIS. 


Description:    Thick,  dark  brown  oil, 
gas;  liquid  at  ordinary  temperature. 
Specific  gravity  at  38°  0. 
Water 
Tar  acids  by  volume 

having  a  very  disagreeable  odor  resembling  Pintsch 

1.041 
Trace 
27.0% 

Fractions 

210  ° 

10.6%   L  quid 

235° 

8.9% 

270° 

12.5% 

315° 

13.1% 

355° 

14.1% 

Res. 

40.4 

Hard 

,  black,  brittle, 

bright  fracture. 

Paraffin  Oils: 

Fractions 

Per  cent  of 

Per  cent  of 

Fraction 

Straight  Oil 

210° 

C 

9,7 

25.0 

2.4 

235° 

9.0 

10.0 

0.9 

270° 

12.3 

10.0 

1.2 

315° 

13.7 

10.0 

1.4 

355° 

15.0 

15.0 

2.3 

59.8 

8.2 

Total 

per  cent  paraffin 

in  fractions  below 

355°  C. 

13.7% 

Total 

per  cent  paraffin 

in  fractions  below 

355°  C.  based  on  whole  oil 

8.2% 

IV.     SUMMARY. 

1.  Coke  of  good  density  and  hardness  may  be  made  by  mixtures 
of  semi-coke  and  raw  coal  if  both  are  finely  divided  and  evenly  mixed. 
A  variation  is  noticeable  in  the  quantity  of  such  non-coking  material 
which  may  be  incorporated  with  different  coals.    For  example,  fresh 
coal  from  Vermilion  County  will  carry  such  an  addition  of  100  per 
cent  of  its  weight  to  advantage.     Coals  from  Saline  and  Williamson 
Counties  give  coke  of  the  highest  density  when  mixed  in  the  propor- 
tion of  50  per  cent  of  their  weight  with  semi-coke. 

2.  The  coke  resulting  from  the  low  temperature  process  has  from 
18  to  22  per  cent  of  volatile  matter  remaining,  but  since  it  has  been 
heated  above  400°  there  should  be  none  of  the  tar  constituents  remain- 
ing.   The  most  convincing  test  on  this  point  as  also  the  best  method  of 
arriving  at  a  conclusion  as  to  its  adaptability  for  such  work  was  to  try 
out  the  material  in  a  suction  gas  producer.    The  results  indicated  that 


3O  OLIN — THE  COKING  OF  COAL 

no  clogging  effect  whatever  results,  thus  showing  the  absence  of  tar 
bodies.  The  physical  operation  of  the  producer  as  well  as  the  grade 
of  the  gas  produced  was  fully  equal  if  not  superior  to  the  perform- 
ance of  the  outfit  when  anthracite  was  used. 

3.  The  semi-coke  has  such  an  amount  of  volatile  matter  remain- 
ing, together  with  the  right  degree  of  coherence  as  to  make  it  especially 
well  adapted  to  household  use.    It  is  clean  to  handle,  free  from  dust, 
and  burns  without  smoke  or  the  formation  of  soot.    Especially  to  be 
noted  in  this  connection  is  its  ability  to  retain  a  fire  without  undue 
attention  as  to  drafts,  etc. 

4.  The  average  specific  gravity  of  the  tar  is  1.069.    It  is  rich  in 
low  boiling  distillate  passing  over  at  210°.     This  product  averages 
18  per  cent  of  the  total.    The  pitch  residue  amounts  to  approximately 
30  per  cent  and  is  remarkably  free  from  precipitated  carbon. 

5.  The  adaptability  of  the  tar  for  wood  preservation  processes 
seems  to  be  indicated  by  the  high  percentage  of  tar  acids.    These  con- 
stituents make  up  from  28  to  30  per  cent  of  the  crude  material.    The 
larger  part,  about  22  per  cent  is  found  in  the  second  distillate  (210°- 
325°),  only  about  7  per  cent  coming  over  below  210°. 

6.  Approximately  10  per  cent  of  the  crude  tar  is  found  to  be  low 
boiling  distillate  free  from  the  tar  acids  and  suitable  for  use  in  in- 
ternal combustion  engines. 

7.  Naphthalene  is  absent.     The  free  carbon  in  the  crude  tar  is 
less  than  2  per  cent  and  the  residual  product  after  the  light  distillate 
and  heavy  oils  are  removed  would  be  classed  as  hard  pitch. 

8.  A  principal  feature  results  from  this  study  of  these  various 
substances,  namely,  that  all  three  of  the  general  divisions  of  coke,  tar, 
and  gas  have  specific  properties  of  an  especially  valuable  sort  which 
would  indicate  that  the  process  of  coking  at  low  temperatures  could 
be  established  successfully  on  a  commercial  basis. 

V.     REVIEW  OF  LITERATURE. 

In  the  effort  to  solve  the  smoke  problem  which  arises  wherever  bitu- 
minous coal  is  extensively  used,  numerous  attempts  have  been  made  to 
modify  the  raw  fuel  in  various  ways  in  order  to  obtain  a  product 
which  should  be  more  or  less  free  from  smoke  producing  constituents. 
Among  the  first  to  make  the  attempt  was  Col.  Scott-Moncrieff,*  who 
proposed  to  subject  coal  to  the  coking  process  in  the  ordinary  gas  re- 

*Jour.  of  Gas  Lighting,    101,  823. 


OLIN — THE  COKING  OF  COAL  3  I 

torts  at  the  usual  temperature  until  one-half  of  the  volume  of  gas  usu- 
ally obtained  was  driven  off.  The  charge  was  then  drawn  and 
quenched. 

The  scheme  resulted  in  failure  for  very  obvious  reasons.  On  ac- 
count of  the  porosity  of  coke  it  is  a  very  poor  heat  conductor  and  so 
the  interior  of  the  charge  received  an  insufficient  amount  of  heat  to 
drive  off  the  tar  and  smoke  producing  substances  while  on  the  other 
hand  the  exterior  was  heated  to  such  a  degree  that  it  became  essen- 
tially hard  gas-coke  which  ignited  with  difficulty  and  burned  slowly. 
A  mass  consisting  of  a  soft  uncarbonized  interior  and  a  hard  shell  was 
the  result,  a  type  of  fuel  which  possessed  no  good  qualities  and  which 
gained  no  popularity.  At  the  same  time  the  manufacturer  lost  one- 
half  of  the  gas  and  much  of  the  ammonia  that  would  be  produced  in 
ordinary  practice. 

*In  1907  a  radical  change  in  the  method  of  heating  was  made  by  W. 
Parker  and  the  product  obtained  was  extensively  advertised  under  the 
trade  name  of  ' '  Coalite. ' '  This  was  the  coke  made  by  the  partial  dis- 
tillation of  slack  coal  in  vertical  oblong  cast  iron  boxes  or  stills  about 
ten  or  twelve  feet  high  and  ten  by  forty-eight  inches  in  cross  section. 
Carbonization  was  carried  on  at  temperatures  near  450°  C,  yielding  a 
coke  having  about  10  per  cent  of  volatile  matter  and  80  per  cent  of 
fixed  carbon. 

The  following  table  shows  the  composition  of  the  gas  obtained  in 
the  distillation. 

TABLE  16. 
COMPOSITION  OF  GAS  OBTAINED  IN  COALITE  MANUFACTURE. 


H2S 
C02 

1.0 
3.45 

H2 
CH4 

14.30 
61.00 

02 

.72 

N2 

9.28 

Ilium. 

4.19 

CO 

6.06 

Coalite  has  not  proved  to  be  the  commercial  success  that  its  pro- 
moters hoped  to  make  it,  but  experimental  work  is  still  being  carried 
on  with  that  end  in  view. 

The  Premier  Tarless  Fuels  Company f  of  Battersea,  England,  have 
lately  installed  a  plant  for  the  production  of  smokeless  fuel  by  low 
temperature  distillation.  The  distinctive  features  are  the  use  of  an- 
nular retorts  which  allow  the  thickness  of  the  charge  to  be  reduced  to 
21/2  inches  and  the  coking  time  to  be  shortened  proportionately,  and 

*Gas  World,  June  8,  1907.    p.  715. 

fJour.  of  Gas  Light  &  Water   Supply.     122,   514. 


32  OLIN — THE  COKING  OF  COAL 

the  maintainance  of  a  reduced  pressure  of  27  inches  in  the  retorts. 
Temperatures  of  about  500°  C  are  used  and  the  charge  is  drawn  at 
the  end  of  four  or  five  hours. 

A  sample  yield  from  a  Lancashire  coal  is  given  below. 

TABLE  17. 
YIELD  OF  PRODUCTS  FROM  VACUUM  PROCESS. 


Tarless  fuel  78.0    per    cent 

Tar  (per  ton  of  coal)  20.19  gal. 

Ammonium  sulphate  (per  ton)  45  Ib. 
Approximate  Composition  of  Fuel 

Fixed  carbon  92.86 
Volatile  matter  3.86 

Ash  3.28 


This  fuel  is  said  to  work  well  in  the  gas  producer.  Another  sample 
with  8.26  per  cent  of  volatile  matter  gives  good  results  when  used  for 
domestic  purposes,  burning  with  a  free  flame,  giving  out  intense  heat 
and  little  smoke. 

In  considering  the  subject  of  tars  and  gases  and  their  relationship 
to  the  matter  of  economy  in  coal  carbonization  no  attempt  will  be  made 
to  review  the  great  mass  of  literature  relating  to  them,  but  merely  to 
call  attention  to  results  which  show  causes  for  variation  in  the  quality 
and  yield,  chief  of  which  are  range  of  distillation  temperatures  and 
differences  in  the  sizes  and  shapes  of  the  retorts. 

The  results  obtained  by  Lewis  P.  Wright,*  published  twenty-five 
years  ago,  show  the  effect  of  increase  in  heat  intensity  in  a  striking 
manner.  He  does  not  state  definitely  the  temperatures  at  which  the 
different  tars  were  produced  but  the  following  table  compiled  from 
his  data  indicates  clearly  that  the  gradations  were  marked. 


TABLE  18. 
RESULTS  OF  FOUR  RUNS  (2cwt.  charges). 


Sp.   Gr.  Tar 

Duration  of 
Distillation 

Gas  Yield  per 
Ton  of  Coal,  Cu.  Ft. 

Free   Carbon    in 
Tar,  Per  Cent 

(1)      1.084 
(2)      1.103 
<3)      1.149 
(4)      1.204 

8  hrs. 
7  hrs. 
6  hrs. 
5  hrs. 

6600 
7200 
8900 
11700 

8.69 
11.92 
15.53 
24.67 

His  analyses  of  the  tars  obtained  show  the  characteristic  increase 
in  volatile  constituents  with  rise  in  distillation  temperature. 


*Jour.   Soc.  Chem.  Ind.   7.   59. 


OLIN — THE  COKING  OP  COAL 


33 


TABLE  19. 
PERCENTAGE  COMPOSITION  BY  WEIGHT  OF  TARS. 


No.  1 

No.  2 

No.  3 

No.  4 

Crude  naptha 

9.17 

9.05 

3.73 

.99 

Light   oil 

10.50 

7.46 

4.47 

.57 

Creosote  oil 

26.45 

25.83 

27.29 

19.44 

Anthracene  oil 

20.32 

15.57 

18.13 

12.28 

Pitch 
Paraffin  contents  of  crude  naptha 

28.89 

36.80 

41.80 

64.08 

(by  volume) 

5.0 

4.0 

1.5 

1.0 

There  is,  likewise,  a  consistent  fall  in  the  percentages  of  the  acid 
in  the  liquid  fraction  as  the  following  table  shows. 

TABLE  20. 
PERCENTAGE  OF  TAR  ACIDS. 


In  Crude  Naptha 

In    Light    Oil 

In  Creosote 

No.   1 
No.  2 
No.   3 
No.  4 

13 
9 
8 
6 

34 
35 
29 
22 

35 

29 
28 
20 

Napthalene  and  anthracene  become  prominent  in  the  heavier  tars 
according  to  his  investigations,  the  former  appearing  in  considerable 
quantity  in  No.  4  and  the  latter  being  at  its  maximum  in  No.  3. 

As  proof  that  the  tendency  of  increased  temperature  in  the  distil- 
lation of  coal  is  to  destroy,  preferably,  the  phenol  bearing  light  oils 
intermediate  between  the  crude  naptha  and  the  creosote,  he  cites  the 
case  of  a  tar  of  specific  gravity  1.33,  distilled  at  high  temperatures, 
which  showed  practically  no  light  oils  but  which  yielded  solid  naptha- 
lene  immediately  after  the  naptha  had  come  over.  Watson  Smith,  in 
an  article  on  "Variation  in  the  Products  of  the  Destructive  Distilla- 
tion of  Coals,"*  confirms  these  results,  by  stating  that  tars  which  were 
produced  at  very  high  temperatures  in  Simon-Carves  ovens  and  exam- 
ined by  him,  showed  a  conspicuous  lack  of  the  middle  oil  fraction 
which  contains  the  phenols  and  that  the  creosote  and  anthracene  oils 
were  semi-solid,  the  former  being  thick  with  napthalene. 

He  calls  attention  to  a  theory  of  Schulzef  that  the  primary  prod- 
ucts of  the  dry  distillation  of  coals  are  phenols.  These  phenols  are 

*Jour.  Soc.  Chem.  Ind.  8,  952. 
tAnnalen,   227,   143. 


34 


OLIN — THE  COKING  OF  COAL 


then  at  the  higher  temperatures  of  the  retorts  split  up  so  as  to  yield 
water  and  high  boiling  hydrocarbons,  or  finally,  with  more  entire  de- 
composition, into  illuminating  gas. 

An  interesting  table  showing  the  effect  of  change  of  temperature 
on  the  yield  of  gas  and  tar  is  given  by  V.  B.  Lewes.* 

TABLE  21. 
VARIATION  OF  GAS  AND  TAR  YIELD  WITH  TEMPERATURE  RANGE. 


Temp.    (C) 

Gas  yield 
per   ton,   cu.   ft. 

Tar 
gallons 

Sp.   gt.   of 
Tar 

900° 

11   000 

9 

1.200 

800° 

10   000 

12 

1.170 

700° 

9   000 

15 

1.140 

600° 

7   750 

18 

1.115 

500° 

6  400 

21 

1.087 

400° 

5   000 

23 

1.060 

Lewes  points  out  that  tars  produced  at  temperatures  between 
400°  C  and  500°  C  contain  relatively  low  percentages  of  aromatic  sub- 
stances and  high  percentages  of  the  paraffin  series  which  are  adapted 
to  use  as  motor  fuels.  The  middle  oils  are  free  from  napthalene  and 
yield  excellent  enriching  oils.  The  pitch  having  practically  no  free 
carbon,  he  says,  forms  an  ideal  electric  insulating  material. 

Variations  in  the  quality  and  composition  of  the  gas  are  shown  in 
the  following  table. 

TABLE  22. 
COMPOSITION  OF  GASES  PRODUCED  AT  DIFFERENT  TEMPERATURES. 


400° 

500° 

600° 

700° 

800° 

900° 

Hydrogen 
Saturated  hydrocarbons 
Unsaturated  hydrocarbons 

21.2 
60.1 
6.3 

28.3 
56.2 
5.8 

33.8 
30.7 
5.0 

41.6 
45.0 
4.4 

48.2 
39.1 
3.8 

54.5 
34.2 
3.5 

The  gas  produced  at  the  lowest  temperatures  quoted  has  a  calorific 
value  of  750  B.t.u.  and  measures  20  candle  power. 

Dr.  H.  W.  Jayne,  in  a  paperf  before  the  Fifth  International  Con- 
gress of  Applied  Chemistry  at  Berlin  in  1903,  says  in  regard  to  coal 
tars: 


*Jour.  of  Gas  Light.      101,   823. 

tThe  Coal  Tar  Industry  in  the  U.  S.     Report  of  the  Fifth  International  Congress  of  Ap- 
plied Chemistry,  Section  IVa,  Volume  II,  p.  721. 


OLIN — THE  COKING  OP  COAL  35 

"The  influence  of  the  temperature  in  carbonizing  is  strikingly 
shown  by  the  test  of  two  tars,  both  from  the  same  coal,  and  made  in 
the  same  kind  of  ovens.  One  plant  was  producing  gas  as  its  main 
object.  The  tar  from  this  source  had  a  gravity  of  1.21  and  tested  17.5 
per  cent  of  free  carbon;  the  light  oil  fraction  was  2.2  per  cent  of  a 
gravity  0.979,  testing  23  per  cent  to  170  deg. ;  the  pressed  napthalene 
yield  was  7.4  per  cent.  In  the  second  tar,  in  which  coke  was  the  main 
object,  evidently  much  lower  heats  were  used,  the  tar  having  a  gravity 
of  1.137,  and  testing  3.2  per  cent  of  free  carbon;  the  light  oil 
amounted  to  11.9  per  cent,  and  had  a  gravity  of  .970,  testing  28  per 
cent  to  170  deg.,  or  six  times  more  crude  naptha  than  in  the  first;  the 
total  tar  acids  were  12.48  per  cent,  while  the  pressed  napthalene  fell 
to  1.2  per  cent."  It  is  evident,  he  thinks,  that  in  the  first  tar  the  light 
hydrocarbons  and  tar  acids  had  been  destroyed  by  the  temperature 
employed,  with  formation  of  napthalene. 

R.  P.  Perry*  states  that ' '  Depending  upon  the  coal  used  and  more 
particularly  upon  the  size  and  shape  of  retorts,  the  travel  which  the 
gases  make  over  the  hot  surfaces,  and  the  temperatures  to  which  the 
gas  is  subjected,  the  coal  tars  vary  within  wider  limits.  In  general 
with  the  vapors  subjected  to  the  high  temperatures  usually  character- 
istic of  gas  works  as  compared  with  coke  works,  there  is  an  increase  in 
specific  gravity  and  free  carbon.  For  example  the  tar  from  many  gas 
works  will  average  about  1.24  specific  gravity  at  15.5°C.  and  about  25 
per  cent  to  30  per  cent  free  carbon  by  weight,  whereas  from  the  by- 
product coke  ovens  the  specific  gravity  would  average  more  nearly 
1.19  and  the  free  carbon  would  vary  about  5  per  cent  to  18  per  cent, 
the  average  being  less  than  10  per  cent. ' ' 

This  so-called  free  carbon  represents  a  finely  divided  inert  ma- 
terial, largely  carbon,  which  is  the  portion  of  tar  insoluble  in  benzol 
and  toluol.  Perhaps  a  very  small  part  is  carried  over  mechanically  in 
the  coking  process,  but  for  the  most  part  it  is  due  to  the  cracking  of 
the  hydrocarbons  by  exposure  to  heat,  and  the  higher  percentage  usu- 
ally found  in  gas  works  tars  is  from  this  cause. ' ' 

S.  R.  Church  of  the  Barrett  Manufacturing  Company,  in  an  inter- 
esting article  on  "Tar  and  Its  By-Products/ 'f  gives  a  table  of  results 
of  analyses  which  were  made  in  his  laboratory,  of  the  typical  coke-oven 
tars  produced  in  the  United  States.  It  is  to  be  noted  that  the  different 

*R.  P.  Perry.  Tar  Distillation  in  the  U.  S.  Eighth  International  Congress  of  Applied 
Chemistry.  10,  233. 

t'Tar  and  Its  By-Products,"   Gas  Age,   May  15,    1913. 


OLIN — THE  COKING  OP  COAL 


gas  retorts  and  ovens  used  vary  in  size  and  shape  and  that  the  former 
are,  of  course,  heated  to  a  much  higher  temperature  than  the  latter. 

TABLE  23. 
ANALYSES  OF  TYPICAL  TARS  ;  DRY  TAR. 


Gas  Retort 

Coke  Oven 

Horizontal 

Inclined 

Vertical 

United 
Otto 

Semet- 
Solvay 

Koppera 

Water  gas 
Eastern 

Specific      gravity      at 

15.5°  0. 
Free     carbon      (insol- 

1.266 

1.293 

1.238 

1.153 

1.207 

1.188 

1.186 

1.083 

uble  in  CeHe) 
Specific   viscosity 

28.8 

37.5 

24.3 

13.3 

10.7 

6.8 

0.1 

(Engler  at   100  °C) 
Oil  to  soft  pitch  60°C. 

21.8 

30 

14.9 

2.1 

3.4 

3 

2.1 

1.6 

(Per    cent    by    vol- 

ume) 
Pitch     residue     60°C. 

13.2 

14.3 

28.8 

21.2 

21.8 

35.3 

43.1 

mp     (Per    cent    by 

volume) 
Refractive    indices    at 

86.8 

85.7 

71.2 

78.8 

78.2 

64.7 

56.9 

60°  C.     (taken     on 

oil) 
Sulphonation     residue 

1.5932 

1.5807 

1.5755 

1.5987 

1.6122 

1.6139 

1.5678 

(Per   cent   taken    in 

oil) 

0.4 

2.4 

4.3 

8 

Tar    acids    (Per    cent 

taken  in  oil) 

14. 

21.0 

29. 

12 

4 

The  figures  given  here  are  especially  significant  when  compared 
with  those  of  low  temperature  tars. 

Vivian  B.  Lewes*  in  the  series  of  articles  mentioned  earlier  says  of 
the  tar  produced  in  the  manufacture  of  coalite,  distilled  at  400°  to 
500°  C. :  "  The  low-temperature  tar  is  distinctive  in  its  characteristics. 
It  has  a  specific  gravity  of  1.075,  is  very  liquid,  and  contains  an  abun- 
dance of  light  solvent  oils,  very  low  aromatic  hydrocarbons,  very  little 
phenol  but  large  quantities  of  cresol,  no  napthalene,  and  very  little  an- 
thracene, while  the  free  carbon  is  as  a  rule  below  two  per  cent. ' ' 

The  very  low  percentage  of  benzene  in  the  light  oils,  is  made  up  for 
by  the  presence  of  paraffins,  such  as  hexane,  heptane  and  octane,  while 
there  are  also  present  considerable  quantities  of  that  curious  group  of 
hydrocarbons  known  as  napthenes  or  hexahydro-benzenes,  which  play 
so  important  a  part  in  Russian  petroleum. 

As  before  mentioned,  carbolic  acid  occurs  in  small  quantities,  but 
its  higher  homologues,  such  as  cresylic  acid,  etc.,  occur  in  much  larger 
quantities  than  in  coal  tar,  and  there  are  also  present  quantities  of 
polydydric  phenols,  or  other  esters  of  the  type  met  with  in  coal  tar 
which  form  resinous  masses  difficult  to  analyze.  He  states  that  coals 
rich  in  oxygen  (10  to  11  per  cent)  and  hydrogen  (above  5  per 

*The  Carbonization  of  Coal.     Lecture  IV.  Jour.  Roy.  Soc.  Arts.  60,  216. 


OLIN THE  COIJING.'OlJ  COAL';';  I';  ^  I  ;    .'. 


37 


cent)  and  which,  therefore,  have  large  percentages  of  resinic  bodies, 
on  being  carbonized  at  low  temperatures  yield  tars  rich  in  phenol  and 
cresol.  These  results  are  confirmed  by  Bornstein.  The  pitch  left  as  a 
residue  amounts  to  about  40  per  cent  of  the  tar,  and  is  of  fine  quality 
owing  to  the  practical  absence  of  free  carbon.  The  ammonium  sulphate 
amounted  to  only  12  Ib.  per  ton  of  coal,  the  temperature  being  too 
low  for  large  production. 

The  tar  yield  varies  with  the  coal  used  and  in  most  cases  averages 
twenty  gallons  per  ton  of  coal. 


TABLE  24. 
COMPOSITION  OF  TAB  FROM  COALITE. 


Specific  Gravity                        1.073 
Distillation  on  2,274  cc.       (0.5  gallon) 

Temp. 

By  volume 
on  tar 

Sp.  gr. 

Volume  of 
hydrocarbons 

Tar  acids 

Water 
Light  Oil 
Carbolic    Oil 
Creosote  Oil 
Creosote  Oil 
Anthracene  Oil 
Anthracene  Oil 

170° 
170°-225° 
225°-240° 
240°-270° 
270°-300° 
300°-320° 
Pitch  by  weight 
Bases 

2.64 
3.10 
13.72 
8.35 
8.35 
8.80 
12.31 
on  volume 

.844 
.959 
.988 
.992 
1.029 
1.033 

3.10 
8.62 
4.64 
5.45 
6.60 
8.80 
41.71% 
1.32% 

4.80 
3.10 
2.55 
1.76 
3.10 

100°  C 

120° 

140° 

170° 

over  170° and 


Light   Oils 

Percentage  distilling  below 
15.6  by  vol. 
31.2 
54.7 
82.8 
17.2 


Calculated  on  Tar 

.55 
1.09 
1.91 
2.90 

.20 


Prevost  Hubbard*  has  lately  published  a  similar  table  of  his  own 
results  obtained  from  the  analyses  of  tars  from  twenty-six  of  the  thir- 
ty-one by-product  coke  ovens  operating  in  this  country  in  1910.  His 
figures  may  be  considered  as  showing  authoritatively  the  character  of 
the  67,000,000  gallons  of  tar  produced  from  these  sources  in  that  year. 

The  specific  gravities  of  the  samples  ranged  from  1.133  to  1.214,  the 
majority  being  lower  than  1.200  and  indicating  low  percentages  of 
free  carbon.  The  minimum  percentage  of  free  carbon  was  2.73,  the 
maximum  16.80,  and  the  average  for  the  26  samples  was  8.38.  Eight- 
een samples  contained  less  than  10  per  cent  of  free  carbon,  and  eight 
samples  more  than  10  per  cent.  About  two-thirds  of  these  products 


*Coke-Oven  Tars  of  the  United  States,  Circular  No.   97.      Office  of  Public  Roads,   U.    S. 
Dept.  of  Agriculture. 


OUN— TftE  COKING  OP  COAL 


might,  therefore,  be  considered  as  low-carbon  tars  and  the  other  third, 
as  medium  carbon  tars. 

In  accordance  with  the  type  of  oven  in  which  these  products  are 
made,  there  is  a  considerable  variation  in  composition,  even  though 
temperatures  differ  but  little.  It  seems  probable,  therefore,  that  high 
pitch  and  free  carbon  contents  are  not  simple  functions  of  tempera- 
ture alone  but  that  other  factors  complicate  the  problem. 


TABLE  25. 
COMPARISON  OF  TARS  FROM  VARIOUS  TYPES  OF  OVENS. 


Kind  of  Oven 

Maximum     Temperature 
of  Retorts    (C) 

Per  Cent 
Free  Carbon 

Per  Cent 
Pitch  Residue 

Koppers 
Semet-Solvay 
United  Otto 
Otto  Hoffman 
Otto  Hoffman  and  United  Otto  (mixed) 
United  Otto  and  Rothenberg  (mixed) 

1100°-1444° 
1050°-1450° 
1220°-1660° 
1000°-1100° 
1000°-1200° 
1000° 

3.38 
6.74 
9.00 
12.16 
12.51 
17.17 

70 
63-79 
69-78 
60-78 
76 
76 

Furthermore,  the  tars  from  different  ovens  of  the  same  type  show 
marked  inconsistencies  in  many  respects.  For  instance,  twelve  tars 
from  as  many  different  Semet-Solvay  plants  in  which  retort  firing  tem- 
peratures were  in  each  case  1050°-1450°  C,  and  maximum  tempera- 
tures to  which  coal  was  brought,  950°-1150°  C,  show  amounts  of  free 
carbon  ranging  from  4  per  cent  to  9  per  cent;  of  pitch,  from  63  per 
cent  to  79  per  cent;  and  of  anthracene  oils,  from  5.5  per  cent  to  11 
per  cent. 

Lunge,*  the  authority  on  coal  tars,  discusses  only  very  briefly  the 
effect  of  temperature  range  on  the  quality  of  tar.  Among  others,  he 
quotes  Behrens,f  who  found  that  the  tar  obtained  in  the  distillation  of 
coal  in  the  ordinary  fire-clay  gas-retorts  was  much  richer  in  benzene, 
tolene,  and  napthalene  than  that  made  from  the  same  kind  of  coal  in 
coke  ovens  operated  at  a  lower  temperature. 

In  considering  and  comparing  the  foregoing  reports  it  should  be 
borne  in  mind  that  as  yet  no  standard  or  official  methods  for  tar  an- 
alysis and  testing  have  been  adopted  by  the  industry  as  a  whole.  It  is 
true,  that  while  the  manufacturers  of  special  products  such  as  creosote 
and  road  material,  each  in  his  own  particular  field  has  defined,  more 
or  less,  his  standards,  the  results  obtained  are  not  always  comparable, 
and  this  is  especially  true  when  dealing  with  such  complex  hydrocar- 

*Lunge,   Coal  Tars  and  Ammonia,  4th  ed.   1909. 
fDingler's  Polytech.   Jour.    208,   862. 


OLIN — THE  COH^G'.&El  C<J^k          :.;  l\l  •  ,*;.  39 

bons  as  coal  tars.  In  spite  of  this  difficulty,  however,  there  is  sufficient 
unanimity  among  the  authorities  to  establish  the  fact  fully  confirmed 
by  the  worker  in  organic  chemistry  that  rise  of  temperatures  tend  to 
produce  polymerization  with  the  formation  of  more  complex  sub- 
stances of  higher  molecular  weight,  and  that  comparatively  valueless 
products  such  as  naphthalene  and  heavy  pitch  are  produced  in  increas- 
ing quantities.  In  other  words,  the  lighter  and  more  valuable  hydro- 
carbons are  being  destroyed  in  favor  of  the  heavier  ones  which  find 
little  industrial  use. 


V7ITA 

The  writer  received  his  elementary  and  secondary  school  training 
in  the  public  schools  of  0  'Brien  County,  Iowa.  In  1908  he  was  grad- 
uated from  the  University  of  Iowa  with  the  degree  of  Bachelor  of  Arts. 
From  1908  to  1910  he  was  instructor  in  Physics  and  Chemistry  in  the 
University  Preparatory  School  of  Oklahoma,  leaving  at  the  end  of  that 
period  to  accept  a  fellowship  in  Chemistry  in  the  Engineering  Experi- 
ment Station  at  the  University  of  Illinois.  He  was  granted  the  de- 
gree of  Master  of  Science  at  Illinois  in  1911.  In  the  year  1913-1914  he 
was  instructor  in  Chemistry  at  Vassar  College  and  at  the  present  time 
holds  a  similar  position  at  the  University  of  Illinois. 

He  has  published  with  Professor  S.  W.  Parr:  "The  Coking  of  Coal 
at  Low  Temperatures  with  a  Preliminary  Study  of  the  By-Products, ' ' 
Bulletin  No.  60,  Engineering  Experiment  Station  of  the  University  of 
Illinois,  1912. 

He  is  a  member  of  Gamma  Alpha,  Phi  Lambda  Upsilon,  Sigma  Xi, 
and  the  American  Chemical  Society. 


LOAN  DEPT 


(CT097slO)47 


Gaylord  Bros. 

Makers 

Syracuse,  N.  Y. 
PAT.  JAN.  21,  1908 


YC  18469 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


